Briefly, explain the differences between a mechanistic approach and a teleological approach to the study of physiology.
• Mechanistic approach: The mechanistic approach to physiology – the study of mechanisms or the “how” things work
For example: “How do red blood cells transport oxygen?” is answered with “Oxygen binds to hemoglobin molecules in the red blood cells” - but this does not provide clarity regarding the value of such transport to the organism
• Teleological approach: The teleological approach to physiology – the study of functions or the “why” things work in a particular way, with an eye to the adaptive significance of a particular organismic process
For example: To avoid dehydration in a hostile condition, the body has specific mechanisms to allow kidneys to produce concentrated urine and conserve body liquids).
- The mechanistic approach to physiology – the study of mechanisms or the “how” things work (e.g. “How do red blood cells transport oxygen?” is answered with “Oxygen binds to hemoglobin molecules in the red blood cells” without clarity regarding the value of such transport to the organism).
- The teleological approach to physiology – the study of functions or the “why” things work in a particular way, with an eye to the adaptive significance of a particular organismic process (e.g. to avoid dehydration in a hostile condition, the body has specific mechanisms to allow kidneys to produce concentrated urine and conserve body liquids). - Answer to this question is giving you the answer for the purpose
What is homeostasis? What is a homeostatic control mechanism and what are the main components and processes of this mechanism?
Homeostasis is the body’s ability to maintain relatively stable internal conditions, in spite of continuously changing external environments.
Homeostasis is not an unchanging state nor equilibrium, but a dynamic steady state; homeostasis is a relatively stable disequilibrium.
Maintains internal stability and is how the organism is maintaining some sense of stability.
Requires finely tuned communication within the body systems. Most homeostatic processes are accomplished by the highly efficient Nervous and Endocrine Systems.
Each of the homeostatic control mechanisms have at least three components involved in regulating a particular variable (factor, event, process) not to stray from a setpoint (optimum value)
a receptor that senses and monitors environmental stimuli
an integrating control center determines needed set point, analyzes input and determines the appropriate response to environmental changes (stimuli)
and an effector offers the means by which the control center responds.
Homeostatic mechanisms rely on response loops (from stimulus to response) and feedback loops who modulate response loops.
Most homeostatic mechanisms are operated through negative feedback loops, which support homeostatic processes; positive feedback loops are rarely homeostatic.
For all practical purposes, all illnesses can be considered as homeostatic imbalances.
- Homeostasis is the body’s ability to maintain relatively stable internal conditions, in spite of continuously changing external environments.
- Homeostasis is not an unchanging state nor equilibrium, but a dynamic steady state; homeostasis is a relatively stable disequilibrium.
- Maintains internal stability and is how the organism is maintaining some sense of stability.
Homeostatic control mechanism:
Requires finely tuned communication within the body systems. Most homeostatic processes are accomplished by the highly efficient Nervous and Endocrine Systems.
- Each of the homeostatic control mechanisms have at least three components involved in regulating a particular variable (factor, event, process) not to stray from a setpoint (optimum value)
1. A receptor that senses and monitors environmental stimuli
2. An integrating control center determines needed set point, analyzes input and determines the appropriate response to environmental changes (stimuli)
3. An effector offers the means by which the control center responds.
Negative feedback: product of the Rx leads to decrease in the Rx
–Homeostatic mechanisms rely on response loops (from stimulus to response) and feedback loops who modulate response loops.
- -Most homeostatic mechanisms are operated through negative feedback loops, which support homeostatic processes; positive feedback loops are rarely homeostatic.
- -For all practical purposes, all illnesses can be considered as homeostatic imbalances.
Stimulus produces change in variable –> change detected by RECEPTOR (sensor) –> input: information sent along afferent pathway to CONTROL CENTER –> output: information sent along efferent pathway to acting EFFECTOR –> response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis
- Describe the various glial cells found in the Nervous System and their functional contributions?
- Astrocytes: (CNS) star-shaped, w/ arm-like extensions; function in protection (BBB); cover the outer surface of blood vessels in the brain and make contact with neurons; role in BBB blocking and allowing passage of chemicals; ability to contract or relax blood vessels based blood flow demands; can modulate neural activity; involved in synaptogenesis; ***involved in scaffolding, immune response, relate interstitial fluid (homeostasis), they prevent large chemicals from leaving the blood vessels and entering the brain, clear out synapses
- Radial glia: astrocyte shoots out extension for a neuron to send axon across to aid in neural growth. After this function is complete, extension withdraws, resumes its function as an astrocyte; progenitor cells that can generate neurons, astrocytes, and oligodendrocytes;
radial migration during neural tube development and later can differentiate (thought to be similar to stem cells)
- Microglia: (CNS); mobile, small; involved with injury or disease by multiplying, engulfing cellular debris or even whole cells, and triggering inflammatory response; recently shown to play role in regulation of cell death, synapse formation, and synapse elimination
- Ependymal cells (CNS): form walls; epithelial lining of ventricle cavities; epithelial layer that surrounds the choroid plexus; and the BBB (+ astrocytes); some have cilia that direct the CSF
- Oligodendrocytes: make myelin sheath of axons inside brain (CNS); cells have extensions that are thick in myelin, these wrap around the axons, creating myelin sheaths
- Schwann cells: make myelin sheath in spinal nerves, cranial nerves (PNS)
- Satellite cells: similar roles to astrocytes in the CNS; supportive cells (PNS)
-Astrocytes: star-shaped, w/ arm-like extensions; function in protection (BBB) & waste ingestion (CNS)
-Radial glia: astrocyte shoots out extension for a neuron to send axon across to aid in neural growth. After this function is complete, extension withdraws, resumes its function as an astrocyte.
-Microglia: (CNS); mobile, small, phagocytosis
form walls; fill spaces between spinal cord & brain structures
-Oligodendrocytes: make myelin sheath of axons inside brain (CNS)
-Schwann cells: make myelin sheath in spinal nerves, cranial nerves (PNS)
-Satellite cells: protective cells (PNS)
Ependymal cells
- Astrocytes- ameobas, give rise to the blood brain barrier, protects brain with extra layer of lipids, protects neuron from any invasions from the circulatory system. provide physical support to neurons and clean up debris within the brain. Forms the blood brain barrier, connecting and protecting the brain from the rest of the body. Has processes that wrap around blood capillaries and other processes wrapped around parts of neurons. Astrocytes receive glucose from capillaries, break it down to lactate and release that into the extracellular fluid that surrounds the neurons. Neurons take the lactate and use it for energy. Neurons receive most of their nutrients from astrocytes. Holds neurons in place. Surround and isolate synapses, limiting the dispersion of NTs that are released by the terminals buttons
- Microglia- smallest of glial cells. Act as phagocytes, engulfing and breaking down dead and dying neurons. They protect the brain from invading microorganisms. (Like mini vacuums).
- Ependymal cells- Creates walls and protect cavities - like epithelial cells. Bubble wrap for the brain.
- Oligodendrocytes- located in CNS - provide support to axons and produce myelin sheath, which insulates most axons from one another.
- Schwann cells- Support axons and produce myelin, but Schwann cells perform their function in the peripheral nervous system. Each segment of an axon is wrapped by one Schwann cell. They aid in digestion of dead and dying axons, and actually aid in regrowth of the axon.
- Satellite cells- Satellite cells are precursors to skeletal muscle cells and are responsible for the ability of muscle tissue to regenerate. Play a crucial role in muscle fiber maintenance, repair and remodeling.
What are the seven common processes involved in neurotransmission? Briefly, explain each process.
- Synthesis (small molecule NTs are synthesized in the cytoplasm)
- Storage (small molecule NTs are packed in synaptic vesicles in the terminal button by the Golgi complex; these vesicles are stored in clusters next to the presynaptic membrane)
- Enzymatic degradation of neurotransmitter leakage from the cytoplasm
- Exocytosis (synaptic vesicles full of NTs hang out near the presynaptic membrane that is full of voltage-activated calcium channels. when stimulated by AP, the channels open, Ca2+ enters the button, causing the vesicles to fuse to the member, releasing the NTs)
- Inhibitory feedback through autoreceptors (negative feedback); (autoreceptors bind to their neuron’s own NT molecules and they are located on the presynaptic membrane; monitor the number of NTs in the synapse; they reduce number when levels are high and increase when levels are low)
- Activation of postsynaptic receptors (NTs produce signals by binding to receptors in postsynaptic membrane; each receptor is a protein that contains binding sites for only particular NTs, only impacts cells with receptors for it; NT is a ligand for its receptor)
- Deactivation by either reuptake (drawn back into the presynaptic buttons by transporter mechanisms) or enzymatic degradation (broken apart by enzymes)
- Synthesis: occurs within presynaptic terminals but enzymes needed for synthesis are made inn soma (cell body)
- Storage: neurotransmitters are packaged in synaptic vesicles that are carried through axon to presynaptic membrane for release into synaptic cleft
- Enzymatic degradation of neurotransmitter leakage from the cytoplasm
- Exocytosis: Process in which neurotransmitters fuses with the presynaptic membrane and empties its contents into the synaptic cleft.
- Inhibitory feedback through autoreceptors (negative feedback): receptors on the terminal button that monitor the presence of the neurotransmitter. When too much is released, the autoreceptor inhibits both production and release. When not enough is released, it raises production.
- Activation of postsynaptic receptors: When neurotransmitters attach to a receptor molecule (complementary binding site) on the target neuron. In ionic receptors, the neuron attaches to the binding site and open ion channels that permit specific ions into cell. With metabotropic receptors, when the neurotransmitter binds w a receptor, a G protein activates an enzyme which produces a second messenger that opens the ion channel.
- Deactivation by either reuptake or enzymatic degradation: Processes in which postsynaptic potentials are terminated when the rate of neurotransmitters released into the synapse exceeds the needed amount. With reuptake, neurotransmitters are recycled from the synaptic cleft back to the terminal button and into the cytoplasm through special transporter molecules. With enzymatic degradation, an enzyme goes into synaptic cleft and destroys the excess neurotransmitters, breaking them down.
Identify the main anatomical and physiological facts indicating the uniqueness of the Central Nervous System in comparison to the others systems in the mammalian body.
- It is the only organ system completely encased by bones and meninges
- Most neurons do not divide through mitosis (amitotic)
- Fat is conducive to brain health
- The blood brain barrier prevents many toxins from entering the brain
- Although it only accounts for 2% of total body weight, CNS uses 15% of body’s total oxygen and about 15% of blood in the body is in the CNS at any one time
-CNS is composed of brain and spinal cord
Brain carries out most complex human functions
Spinal cord is like a 2-way signal between brain and rest of body (also acts independent of brain at times to move muscles)
-Both are completely encased by bones (skull and vertebral column) and meninges
-The brain is the most protected organ in the body, encased with meninges and CSF
-Most neurons in CNS are amitotic (do not divide through mitosis)
-Bundles of myelinated axons are called tracts (in the CNS)
-Brain receives a copious amount of blood supply and is guarded by the Blood-Brain Barrier.
-The CNS is about 2% of body weight; however, the CNS consumes 15% to 20% of the oxygen distributed by the circulatory system (in any given millisecond, 15% to 20% of the body blood flow is in the CNS). This is unique bc other parts of body receive varying quantities dependent on need.
It is the only organ system completely encased by bones and meninges
Most neurons do not divide through mitosis (amitotic)
Fat is conducive to brain health
The blood brain barrier prevents many toxins from entering the brain
Although it only accounts for 2% of total body weight, CNS uses 15% of body’s total oxygen and about 15% of blood in the body is in the CNS at any one time
Describe the main structural and physiological differences between the Sympathetic and the Parasympathetic divisions of the Autonomic Nervous System.
- Point of exit - The Sympathetic division exits through the thoracolumbar system, and the parasympathetic exits either through the cervical region and sacral region.
- Length of the presynaptic axon - In the sympathetic division, the presynaptic axon is myelinated and short as opposed to the parasympathetic nervous system the presynaptic axon is unmyelinated and long.
- Neurotransmitters - sympathetic division utilizes acetylcholine in preganglionic synapse and norepinephrine and/or epinephrine at the organ, whereas the parasympathetic division uses acetylcholine at all synapses.
- Actions at end organ sites (antagonistic) - contribution of the sympathetic division is to prepare for action (i.e., fight, flight, or freeze) (e.g., dilates pupils, increase metabolic rate, increase rate and force of heart rate, etc.).
- The main functional contributions of the parasympathetic division is to return to a normal state after fight, flight, or freeze (e.g., constricts pupils, decreases heart rate to be slow and steady, etc.)
Structural:
- Part of spinal cord they exit (parasympathetic is cervical and sacral; sympathetic is thoracic and lumbar)
- Parasympathetic synapses (aka ganglion) are closer to the effector organ (sympathetic are closer to the CNS in the adrenal medulla)
- Parasympathetic axons are unmyelinated (both are unmyelinated postganglionic)
Physiological:
4. always starts with Acetylcholine (para stays with acetycholine because it is an inhibitor; sympathetic changes to norepinephrine because int is excitatory)
Sympathetic systems stimulate, organize, and mobilize energy in threatening situations; changes are indicative of psychological arousal (e.g., dilates pupils, inhibits salivary glands, decrease urine output)
Parasympathetic systems: conserve energy; indicative of psychological relaxation (e.g., constricts pupils, decrease heart rate)
Point of exit - The Sympathetic division exits through the thoracolumbar system, and the parasympathetic exits either through the cervical region and sacral region.
Length of the presynaptic axon - In the sympathetic division, the presynaptic axon is myelinated and short as opposed to the parasympathetic nervous system the presynaptic axon is unmyelinated and long.
Neurotransmitters - sympathetic division utilizes acetylcholine in preganglionic synapse and norepinephrine and/or epinephrine at the organ, whereas the parasympathetic division uses acetylcholine at all synapses.
Actions at end organ sites (antagonistic) - contribution of the sympathetic division is to prepare for action (i.e., fight, flight, or freeze) (e.g., dilates pupils, increase metabolic rate, increase rate and force of heart rate, etc.). The main functional contributions of the parasympathetic division is to return to a normal state after fight, flight, or freeze (e.g., constricts pupils, decreases heart rate to be slow and steady, etc.)
Structural Differences:
Sympathetic: Neuronal cell bodies of SNS are located in thoracic and lumbar regions (mostly in thoracic region: T1-T12). Fibers of preganglionic neurons exit ventral roots of spinal cord and pass into sympathetic ganglia of the sympathetic chain (individual sympathetic ganglia are connected along spinal cord). All preganglionic neurons connect w postganglionic neurons which then send axons to the target organs. (pg 85 of C &B has good graphic of this). The terminal buttons on preganglionic axons secrete acetylcholine to terminal buttons on either:
a ganglion which then secretes norepinephrine on target organs
preganglionic axon →ACh → postganglion → norepinephrine
adrenal medulla cells to secrete norepinephrine and epinephrine on target organs.
preganglionic axon →ACh → adrenal medulla → norepinephrine and epinephrine
Parasympathetic: Cell bodies are located in cervical and lumbar regions: nuclei of some cranial nerves (vagus nerve) and in the sacral region of spinal cord. Postganglionic nuerons are located in the immediate vicinity of the target organs. Terminal buttons in both pre and postganglionic neurons secrete acetylcholine (ACh).
preganglionic axon → ACh → postganglion → ACh
Physiological Differences: Basic differences between these two sxs is how they use the circulatory sxs
Sympathetic: Most involved in activities associated with expenditure of energy from reserves that are stored in the body, especially in response to stressors. When the organism is excited, the SNS is responsible for the “fight” reactions in the fight or flight system:
increases blood flow to muscles,
dilates pupils
stimulates secretion of epinephrine (increased heart rate, rise in blood sugar)
causes pilorection (goosebumps)
stimulates sweating
inhibits digestive sx, saliva and tears
stimulates orgasm
relaxes bladder
Parasympathetic: Supports activities involved with increases of the body’s stored energy. It allows system to rest and recover following activation by SNS.
produces tears, constricts pupils
stimulates salivation
slows heartbeat
stimulates digestive sxs
contracts bladder- increases need to urinate
stimulates sexual arousal
In class we discussed the three principles of sensorimotor functions. Describe these principles and propose at least on functional ramification for each of these principles.
- Sensorimotor system is hierarchically organized – info flows from highest to lowest level of operation using multiple paths, while maintaining functional segregation of its neuronal units
- -ramifications: System is adaptable and plastic, capable of acting with various degrees of involvement from the executive suite (cortex)
Hierarchy–pyramid
- levels of operation
- multiple pathways (each is specified but they can be interconnected)
- functional segregation
- Motor output is guided by sensory input – the efficiency and goal-directedness of each movement is guided by a systemic use of continuous sensory feedback
- -ramifications: Sensory and motor are constantly informing each other such (e.g. vision may require moving eyes; grabbing something involves feeling and sensing it)–sensory feedback
Output + input work together
- need to work together
- cant move mouth if numb
- movement is an integration of motor and sensory
- Learning changes the nature and locus of sensorimotor control – learning and practice allows the system to organize responses in continuous sequences of action responding appropriately to sensory feedback without conscious regulation
- -ramifications: Can develop internal schemas and muscle memory once we have developed proficiency in a task. At that point, can be disrupted by “overthinking”
Muscle memory
- during learning learning, cortex is constantly activated
- highly learned, less cortex, subcortical structures take over
- it means your cortex is free for new information–develop internal schema (adaptation)
- Sensorimotor system is hierarchically organized – info flows from highest to lowest level of operation using multiple paths, while maintaining functional segregation of its neuronal units
ramifications: System is adaptable and plastic, capable of acting with various degrees of involvement from the executive suite (cortex) - Motor output is guided by sensory input – the efficiency and goal-directedness of each movement is guided by a systemic use of continuous sensory feedback
ramifications: Sensory and motor are constantly informing each other such (e.g. vision may require moving eyes; grabbing something involves feeling and sensing it) - Learning changes the nature and locus of sensorimotor control – learning and practice allows the system to organize responses in continuous sequences of action responding appropriately to sensory feedback without conscious regulation
ramifications: Can develop internal schemas and muscle memory once we have developed proficiency in a task. At that point, can be disrupted by “overthinking” - The sensorimotor system is hierarchically organized – information flows from the highest to the lowest level of operation utilizing multiple paths, while maintaining functional segregation of its neuronal units. This means the highest level is the association cortex and lowest level is the muscles. There is parallel structure and signals flow between levels over multiple paths.
- Motor output is guided by sensory input – the efficiency and the goal-directedness of each movement is guided by a systemic use of continuous sensory feedback. For example reacting to noise or reacting to a hot stove.
- Learning, changes the nature and locus of sensorimotor control – learning and practice allows the system to organize responses in continuous sequences of action responding appropriately to sensory feedback without conscious regulation. For example when you originally learned how to text on your phone vs now. This minimizes higher level movement in minor level tasks.
What are the main functions and systemic contributions of the musculature system?
a. Producing Movement – almost all movements in the body (mobility, manipulation, quick responses to environmental events, emotional expressions, mobilization of visceral organs and motility of fluids and substances) are produced by muscles.
b. Maintaining Posture – we are usually unaware how the skeletal muscles are continuously making numerous tiny adjustments to maintain appropriate posture in response to the force of gravity.
c. Stabilizing Joints – a by product of the harmonious relationships between muscle, tendons and bones.
d. Generating Heat – as ATP (adenosine triphosphate provides a form of chemical energy used by cells) powers muscle contractions, about ¾ of its energy escapes as heat. Heat is vital in maintaining body temperature. Skeletal muscles activity is responsible for 40% of body heat.
- Movement–skeletal muscles enable joint movement, facial expressions and respiratory muscles enable breathing
- Support- Muscles support all internal organs
- Protection–skeletal muscles protect the body’s internal organs
from force. - Heat generation–Heat is a waste product of muscle metabolism, which helps maintain an internal body temperature of 98.6 F.
- Blood circulation–Cardiac muscles aid pumping action of the heart by aiding blood circulation.
Contraction: shortening and lengthening of muscle fibers to produce and control all body movements
Manipulating the environment
Maintaining posture: numerous tiny adjustments to respond to gravity
Joint stabilization: A process occurring with the simultaneous contributions of the muscular and skeletal systems and tendons
Generating heat: ATP powers contractions and the majority of its energy is lost as heat, skeletal muscle responsible for 40% of body heat
Identify three examples of antagonistic hormonal processes. Briefly, present the physiological values specific to each of the antagonistic processes.
Antagonistic hormones oppose the actions of one another.
- GH (Growth Hormone) and ACTH (Adrenocorticotropic) - GH stimulates growth, regeneration, and cellular reproduction, and is usually active at night; ACTH breaks things down and uses energy during times of stress and is usually active during the day. Antagonistic use of energy mobilization (ACTH) and storage (GH).
- Insulin and Glucagon - Insulin transfers glucose out of blood and into hungry cells (unused glucose is converted to Glycogen and transferred for short-term storage in liver), while glucagon transfers glucose out of cells and into the blood when blood insulin levels are low. Following a meal, insulin is active, while glucagon is active in the fasting phase.
- *both pancreatic hormones
3. Parathyroid hormone and calcitonin – when Ca2+ levels are low, PTH (from parathyroid glands) signals osteoclasts to degrade bone matrix and release calcium from bones/teeth back into the blood for use by brain and muscles; when Ca2+ levels are high, calcitonin (from thyroid gland) mobilizes calcium from the blood towards bones and teeth towards salt deposits in bone
4. Prolactin and estrogen - prolactin promotes lactation and produces milk in the mammary glands in response to giving birth, which antagonizes estrogen. The body suppresses the process of preparing for pregnancy and thus lowers its estrogen production. This is why lactation acts as a natural birth control.
One example would be Parathyroid Hormone and Calcitoin. Calcitonin and PTH are referred to as antagonistic hormones, as their actions are diametrically opposite. While calcitonin is secreted when blood calcium level is extremely high, PTH is secreted when the blood calcium level is too low. Both these hormones are known to regulate the Ca++ levels in blood. Calcitonin is released and produced by the thyroid gland found in the neck while the parathyroid gland is released and produced by the parathyroid gland seen in the thyroid gland.
Another example would be glucagon and insulin. Alpha cells secrete glucagon, beta cells secrete insulin. Glucagon facilitates the release of glucose into the bloodstream from the stored glycogen through a process of signal transduction. Insulin facilitates the elimination of glucose from the bloodstream to store as glycogen through signal transduction.
- GH and ACTH - GH stimulates growth, regeneration, and development and is usually active at night; ACTH breaks things down and uses energy during times of stress and is usually active during the day. Antagonistic use of energy mobilization (ACTH) and storage (GH).
- Insulin and Glucagon - Insulin transfers glucose out of blood and into cells, while glucagon transfers glucose out of cells and into the blood. Following a meal, insulin is active, while glucagon is active in the fasting phase.
- Parathyroid hormone and calcitonin - PTH pulls calcium from bones/teeth back into the blood for use by brain and muscles; calcitonin mobilizes calcium from the blood towards bones and teeth.
- Prolactin and estrogen - prolactin promotes lactation and produces milk in the mammary glands in response to giving birth, which antagonizes estrogen. The body suppresses the process of preparing for pregnancy and thus lowers its estrogen production. This is why lactation acts as a natural birth control.
Discuss main regulatory processes controlling hormonal release into the circulatory system. Include in your answer various modes of stimulation that activate secretion by endocrine glands.
Hormones are usually secreted by ductless glands and distributed via the circulatory system. The main regulatory process controlling hormonal release is a negative feedback loop. The three types of stimuli that act as triggers…
1. Hormonal: hypothalamus secretes hormones that stimulate the anterior pituitary gland to secrete hormones released into the circulatory system that travels to other glands (thyroid gland, adrenal cortex, gonads) and stimulates them to secrete other hormones
- Humoral: the trigger comes directly from the circulatory system, the low concentration of calcium ions stimulates the parathyroid glands to release parathyroid hormone (PTH) directly back into the circulatory system.
- Neural: sympathetic NS arouses adrenal medulla, which then secretes catecholamines (adrenaline/norepinephrine); preganglionic SNS fiber stimulates adrenal medulla cells to secrete catecholamines
Hormones are usually secreted by ductless glands and distributed via the circulatory system. The main regulatory process controlling hormonal release is a negative feedback loop. The three types of stimuli that act as triggers are hormonal, neural, or humoral. With neural stimuli, sympathetic NS arouses adrenal medulla, which then secretes catecholamines (adrenaline/norepinephrine). With hormonal stimuli, anterior pituitary gland stimulates a hormone released into the circulatory system that travels to other glands (thyroid gland, adrenal cortex, testis) and stimulates them to secrete other hormones. With humoral stimuli, where the trigger comes directly from the circulatory system, capillaries enter parathyroid glands, and communicate the status of CA+ ions. The low concentration of calcium ions in the blood stimulates the parathyroid
Per the lecture, the main regulatory process that controls hormonal release into the circulatory system consists of a negative feedback loop mechanism. This feedback loop communicates the status of a hormone with the brain so as to activate necessary processes to restore hormonal imbalances. The triggers for this process (i.e., internal or external stimuli) may be hormonal, neural, or humoral.
Hormonal:
The hypothalamus secretes hormones that stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands (i.e., thyroid gland, adrenal cortex, gonad) to secrete hormones.
Humoral:
Capillary blood contains low concentration of Ca2+ (i.e., Calcium ions), which stimulates secretion of parathyroid hormone (PTH) by parathyroid glands.
This is the most common of processes.
Neural:
Preganglionic SNS fiber stimulates adrenal medulla cells to secrete catecholamines.
How does the brain know stimulus properties acting on sensory organs?
The process of sensation and perception
1. Sense: sense the environmental stimuli using sensory organs which collect filter and amplify information.; the process of detecting the presence of stimuli; process of informing the brain about its environment
- Percept: the final mental representation of the original environmental stimuli; the higher-order process of integrating, recognizing, and interpreting patterns of sensation
- Transduction: conversion of stimuli detected in receptor cells to electrical impulse which are transported by the nervous system; changing a sensory signal to an electrical signal
Specificity of various factors
Stimulus type: specialized sensory neurons
Stimulus location: innervation of distinct areas (myotomes and dermatomes)
Intensity: firings (activations per second)
Duration: duration of action potential in the primary sensory neuron
Transduction: transformation of stimuli into nervous impulse
Type of stimulus or activity is translated by receptor specificity (chemoreceptors, mechanoreceptors, photoreceptors, thermoreceptors, nociceptors)
Stimulus location – point by point innervation (receptive and cortical fields)
Stimulus intensity – firing per second
The more intense a stimulus is the more rapidly the neurons will fire
Stimulus duration – duration of action potentials in the primary sensory neurons
How long the receptors are activated, it will send this information to the cortex, and the cortex will have an equivalent response to this
Transduction
How the brain knows that we need to translate the physical properties from the outside world to neuronal language
Adaptation
Tells us that the nervous system likes to operate in a range of differences
Successive levels of processing
Processing of sensory information by the time it reaches the level of perception happens at at least three places/level
And each level is really important and adds to the final perception that we receive
Attention
Attention is involved in everything we do and is highly shaped by life experiences (because what is important for me is not important to you)
The process by which the nervous system is directing itself to point of focus
Like when we hear a loud noise and our heads turns there automatically
Bi-directionality and inter-connectivity of neural connections (older we are, the information is bi-directional)
a. Explain the differences between sensation and perception. b. Different individuals can have a different sensation in response to the same environmental stimulus, as well as different perceptions of this stimulus. Identify one a common factor causing different sensations in response to the same stimulus, and another factor involved in different perceptions of the same stimulus.
Part A:
Sensation refers to the initial step in the perception process. Per the lecture, environmental stimuli act upon sensory organs which collect, filter, and amplify information obtained through the environment.
Perception refers to the way in which the above information is used; that is, perception is the process in which the brain is informed about its environment.
Part B:
Different Perceptions of Same Stimulus:
A percept refers to the “final mental representation of the original stimulus that triggered the process of perception.” One of the reasons that it is possible for two different individuals to experience different perceptions of the same stimulus is that the percept is the combination of the properties of the stimulus itself and any form of personal meaning that is ascribed to the stimulus (i.e., from one’s previous learning, experiences, and affect).
Different Sensations in Response to the Same Stimulus:
(Am not fully sure about this part) Our attention to particular stimuli is shaped by our life experiences; that is, what is important for one person may not be important for another, which results in differences in what we attend to. For example, someone entering an unfamiliar environment may spend greater time attending to a visual stimulus than someone else who is familiar with the same environment and the same stimulus.
(Another potential) The same stimulus may be experienced through multiple different senses simultaneously. For instance, food is often experienced through our sense of taste and smell, which allow for the experience of flavor.
