define the nervous system
it is the body’s complex network of nerve cells (neurons) and supporting cells (glial cells) that coordinate and regulate bodily functions. It includes the central nervous system and the peripheral nervous system. The nervous system processes sensory input, initiates responses, and controls movements, thoughts, emotions, and physiological processes throughout the body.
name four glial cells and their functions
- Astrocytes
Function: Provide structural support to neurons, regulate the extracellular environment, maintain the blood-brain barrier, and participate in synaptic transmission. - Oligodendrocytes (CNS) / Schwann cells (PNS):
Function: Produce myelin to insulate axons and facilitate faster transmission of electrical impulses. - Microglia:
Function: immune cells of the CNS, phagocytosing pathogens and cellular debris, and participating in neuroinflammation and tissue repair. - Ependymal cells:
Function: Line the ventricles of the brain and central canal of the spinal cord, producing cerebrospinal fluid (CSF) and contributing to the blood-CSF barrier.
what are basic functions of a neuron
- Transmission of Electrical Signals
- Integration of Information
- Propagation of Signals
- Release of Neurotransmitters
- Modulation of Signal Strength
- Plasticity and Adaptation
- Regulation of Physiological Processes
describe three functional classes of neurons
- Sensory Neurons (Afferent Neurons):
transmit signals from sensory receptors (e.g., in the skin, eyes, ears, taste buds) to the central nervous system - detect stimuli such as light, sound, touch, temperature, and chemicals, converting these stimuli into electrical signals - Interneurons (Association Neurons):
located entirely within the central nervous system and serve as the intermediaries between sensory neurons and motor neurons. - Motor Neurons (Efferent Neurons):
transmit signals from the central nervous system to muscles, glands, and other effector organs.
They stimulate muscle contraction (skeletal muscles) or glandular secretion (glands)
describe myelination role and process in the central nervous system
role: Oligodendrocytes wrap around multiple axons, forming segments of myelin sheath along the axons. Myelination serves to insulate and electrically isolate axons, allowing for faster and more efficient transmission of electrical impulse also provides structural support to axons
Process: Oligodendrocytes wrap around axons. The myelin sheath is interrupted by small gaps called nodes of Ranvier, where the axon membrane is exposed. begins during late embryonic development and continues into early adulthood.
Myelination is regulated by various signaling molecules and interactions between oligodendrocytes and axons. Disruption of this process can lead to neurological disorders such as multiple sclerosis.
outline major branches of central nervous system
CNS
Brain:
- divided into several regions, including the cerebrum, cerebellum, and brainstem.
- Responsible for processing sensory input, initiating motor responses, and higher cognitive functions such as thinking, memory, and emotion.
- Regulates involuntary processes such as heartbeat and respiration.
Spinal Cord:
- A long, tubular structure that extends from the base of the brain down the vertebral column.
state differences between white and grey matter in the central nervous system
White Matter:
Composition: White matter consists mainly of myelinated axons. These axons are surrounded by glial cells, including oligodendrocytes in the CNS.
Color: White matter appears white due to the high lipid content of myelin.
Function: White matter serves as a communication pathway within the CNS. It facilitates rapid transmission of electrical signals over long distances.
Location: White matter is typically located deep within the brain. In the spinal cord, it is found on the outer regions.
Gray Matter:
Composition: Gray matter consists mainly of neuronal cell bodies/dendrites/unmyelinated axons/glial cells. It lacks myelin.
Color: Gray matter appears grayish-brown due to the presence of neuronal cell bodies and neuropil.
Function: Gray matter is primarily involved in information processing and integration within the CNS. Gray matter regions also serve as sites for synaptic connections and neuronal communication.
Location: Gray matter is found on the outer surface of the brain (cerebral cortex). In the spinal cord, gray matter forms an H-shaped region centrally located.
name the three regions of the brain
forebrain - cerebrum, thalamus and hypothalamus
midbrain - tectum, tegmentum and cerebral peduncles
hindbrain - cerebellum, pons and medulla oblongata
name the four lobes of the cerebrum and their function
- Frontal Lobe:
Located: front of the brain.
Functions:
- Motor control: Initiating voluntary movements and coordinating complex motor tasks.
- Executive functions: Higher cognitive processes such as planning, decision-making, problem-solving, and goal-setting.
- Speech production (Broca’s area): Controlling the muscles involved in speech production. - Parietal Lobe:
Located: top of brain, behind the frontal lobe.
Functions:
- Sensory processing: Integrating sensory information from touch, temperature, pain, and proprioception (awareness of body position).
- Spatial awareness and perception: Processing visual information to perceive the location and orientation of objects in space. - Temporal Lobe:
Located: sides of the brain, beneath the lateral fissure.
Functions:
- Auditory processing: Processing auditory information (sound recognition/localization/comprehension of speech)
- Memory formation: Consolidating short-term memories into long-term memories and retrieving stored memories.
- Language comprehension (Wernicke’s area): Understanding spoken and written language. - Occipital Lobe:
Located: back of the brain, behind the parietal and temporal lobes.
Functions:
- Visual processing: Receiving and processing visual information from the eyes (color/shape/motion/depth perception)
- Visual association: Integrating visual information to recognize objects, faces, and scenes.
name two key brain structures in the diencephalon
- Thalamus:
Located: top of the brainstem, below the cerebral hemispheres.
Functions:
- relay station for sensory information, receiving signals from sensory pathways (except olfaction) and transmitting them to the appropriate regions of the cerebral cortex for further processing.
- Involved in regulating consciousness, alertness, and attention. - Hypothalamus:
Located: below the thalamus.
Functions:
- Regulation of homeostasis
- Regulation of the autonomic nervous system - Influencing heart rate, blood pressure, and gastrointestinal motility.
- Endocrine regulation: Producing and releasing hormones
- Regulation of emotional responses and behavior: stress responses, aggression, and sexual behavior.
what hindbrain region controls voluntary movements
cerebellum
what branch of nervous system controls rate and force of contraction of the heart
autonomic nervous system (ANS)
name three types of sensory receptors and their stimulus
- Mechanoreceptors:
Stimulus: Mechanical forces such as pressure, touch, vibration, stretch, or movement. - Chemoreceptors:
Stimulus: Chemical substances in the environment or within the body, such as odorants, tastants, pH, or concentrations of specific ions (e.g., oxygen, carbon dioxide, glucose). - Photoreceptors:
Stimulus: Electromagnetic radiation in the form of visible light
four opposing processes that are regulated by the sympathetic and parasympathetic
- Heart Rate:
- Sympathetic Nervous System: Increases heart rate (positive chronotropic effect).
- Parasympathetic Nervous System: Decreases heart rate (negative chronotropic effect). - Pupil Size (Pupillary Diameter):
- Sympathetic Nervous System: Dilates pupils (mydriasis).
- Parasympathetic Nervous System: Constricts pupils (miosis). - Digestive Activity:
- Sympathetic Nervous System: Inhibits digestive activity
- Parasympathetic Nervous System: Stimulates digestive activity - Respiratory Rate:
- Sympathetic Nervous System: Increases respiratory rate and depth (stimulates bronchodilation).
- Parasympathetic Nervous System: Decreases respiratory rate and depth (stimulates bronchoconstriction).
define an action potential
An action potential is a rapid change in the electrical charge of a neuron or muscle cell. It involves a brief depolarization followed by repolarization, allowing for the transmission of electrical signals along the cell’s length.
what is the membrane potential and describe how its generated
- It is the difference in electrical charge across the cell membrane of a neuron or other excitable cell.
The generation of it is primarily due to the uneven distribution of ions across the cell membrane and the selective permeability of the membrane to these ions. - Sodium-Potassium Pump:
it actively transports sodium ions out of the cell and potassium ions into the cell against their concentration gradients. This requires energy in the form of ATP and helps maintain the concentration gradients of sodium and potassium ions across the membrane. - Ion Channels:
such as voltage-gated ion channels and leak channels, allow ions to move across the membrane down their concentration gradients. - Selective Permeability:
The cell membrane is selectively permeable to different ions. For example, the resting membrane permeability to potassium ions is much higher than that to sodium ions, contributing to the resting membrane potential being closer to the potassium equilibrium potential.
describe how an action potential is generated and how it is propagated along an axon
- Resting Membrane Potential:
At rest, a negative resting membrane potential (-70 millivolts (mV)) - Depolarization:
When a stimulus depolarizes the axon membrane to a threshold level (usually around -55 mV), voltage-gated sodium channels open rapidly. rapid influx of positive charge causes the membrane potential to become more positive (+30 mV)
- Repolarization:
after reaching its peak, voltage-gated sodium channels close, and voltage-gated potassium channels open. Potassium ions move out of the cell, restoring the negative membrane potential (resting level).
- Hyperpolarization:
Sometimes, the membrane potential briefly becomes more negative than the resting level during repolarization due to the prolonged opening of potassium channels
- Propagation:
The action potential generated at one point on the axon triggers the opening of voltage-gated sodium channels in the adjacent region of the axon membrane. This continues sequentially down the length of the axon. The action potential is propagated along the axon in one direction only, from the axon hillock (the initial segment) toward the axon terminals.
describe myelination role and process in the peripheral nervous system
Role: Schwann cells wrap around individual axons to form segments of myelin sheath. Myelination in the PNS serves the same purposes as in the CNS myelination also aids in the regeneration of damaged axons by providing a scaffold for axonal growth and guidance.
Process: During development, Schwann cells extend processes to envelop axons, forming compact myelin sheaths around them. Unlike oligodendrocytes, each Schwann cell myelinates only a single axon segment. myelination in the PNS begins during fetal development and continues postnatally, regulated by various growth factors and signaling molecules, as well as interactions between Schwann cells and axons.
outline major branches of peripheral nervous system
- Somatic Nervous System (SNS):
- Controls voluntary movements and transmits sensory information from the body’s external environment to the CNS.
- Comprises sensory neurons that convey information from sensory receptors (e.g., skin, muscles) to the CNS and motor neurons
2.Autonomic Nervous System (ANS):
- Regulates involuntary physiological processes, including heart rate, digestion, respiratory rate, and glandular secretion.
- Divided into two main branches: the sympathetic nervous system and the parasympathetic nervous system.
a. Sympathetic Nervous System: Prepares the body for “fight or flight” responses, increasing heart rate, dilating airways, and redirecting blood flow to muscles.
b. Parasympathetic Nervous System: Promotes “rest and digest” activities, such as slowing heart rate, stimulating digestion, and conserving energy. - Enteric Nervous System (ENS):
- neurons in the walls of the gastrointestinal tract.
- Regulates digestive processes, including peristalsis, secretion of digestive enzymes, and blood flow to the digestive organs.
- Functions semi-autonomously but also receives input from the CNS via the autonomic nervous system.
what are the cell types of the nervous system
neurons - send electrical impulses
glial cells - support neuron function
what are nerve impulses (action potential)
nerve impulses cause the voltage to swing rapidly positive and then negative
what is resting potential
the voltage measured across the membrane of a neuron when at rest - 65mV
what is depolarization
the inside of the membrane becomes less negative
causes a flood of NA to enter cell from outside
what is repolarization
the membrane returns to its resting membrane potential
causes K to leave the cell so it becomes more positive outside
