Chapter 8 (mod 4)

Question 1

Function of the nervous system

Answer 1

1. receiving sensory input
2. integrating information
   - brain and spinal cord process sensory input and initiate responses
   - may produce an immediate response, be stored as a memory, or be ignored
3. controlling muscles and glands
   - skeletal muscles normally contract only when stimulated by the nervous system
   - controls cardiac muscles, smooth muscles, and many glands
4. maintaining homeostasis
   - ability to detect, interpret, and respond to internal and external conditions
5. establishing and maintaining mental activity
   - the brain is the centre of mental activity, including consciousness, memory, and thinking

Question 2

divisions of the nervous system

Answer 2

1. central nervous system (CNS)
   - brain and spinal cord
2. peripheral nervous system (PNS)
   - all the nervous tissues outside the CNS, including nerves and ganglia

Question 3

divisions of the PNS

Answer 3

PNS is the communication link between the CNS and the various parts of the body
- PNS carries info about different tissues of the body to the CNS and delivers commands from the CNS to other body tissues that alter body activities
1. the sensory division (afferent/toward division)
- conducts action potentials from sensory receptors to the CNS
- the neuron’s that transmit action potentials from the periphery to the CNS are called sensory neurons
2. the motor division (efferent/away division)
- conducts action potentials from the CNS to effector organs, such as muscles and glands
- the neuron’s that transmit action potentials from the CNS toward the periphery are called motor neurons

Question 4

the motor division subdivisions

Answer 4

• effectors controlled by the motor division include muscle tissue and glands - skeletal muscles are voluntarily controlled and cardiac and smooth muscles and glands are involuntarily controlled
  1. somatic nervous system
• transmits action potentials from the CNS to the skeletal muscles
  2. autonomic nervous system (ANS)
• transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands
• this system divides into sympathetic an parasympathetic divisions

Question 5

enteric nervous system (ENS)

Answer 5

• part of the peripheral nervous system (PNS)
• has both sensory and motor neurone contained wholly within the digestive tract
• can function without input from the CNS or other parts of the PNS, although it is normally integrated w the CNS by sensory neurone and ANS motor neurons
• consists of plexuses w/in the wall of the digestive tract
• plexuses include (1) sensory neurons that connect the digestive tract to CNS, (2) sympathetic and parasympathetic neurons that connect the CNS to the digestive tract, (3) enteric neurons, located entirely w/in the enteric plexuses

Question 6

neurons

Answer 6

or nerve cells, receive stimuli, conduct action potentials (electrical signals), and transmit signals to other neurons or effector organs
3 parts:
1. a cell body
- contains a single nucleus - source for gene expression
- rough ER, Golgi apparatus, and mitochondria surround nucleus
- large numbers of neurofilaments and microtubules organise the cytoplasm into distinct areas
2. dendrites (type of processes)
- short, highly branching cytoplasmic extensions that are tapered from their bases at the neuron cell body to their tips
- most extend from neuron cell body but some also project from the peripheral ends of some sensory axons
- receive information from other neurons or from sensory receptors and transmit the information toward the neuron cell body
3. axons (type of processes)
- a single long cell process extending from the neuron cell body
- the area where the axon leaves the neuron cell body is called the axon hillock
- axons of sensory neurons conduct action potentials towards the CNS
- axons of motor neurons conduct action potentials away from the CNS
- axons conduct action potentials from one part of the brain or spinal cord to another part
- axon may remain unbranched or may branch to form collateral axons
- axons can be surrounded by myelin sheath

Question 7

multipolar neuron

Answer 7

• many dendrites on one axon
• most motor neurons and most CNS neurons

Question 8

bipolar neuron

Answer 8

• one dendrite and one axon
• found in special sense organs, such as eye and nose

Question 9

pseudo-unipolar neurons

Answer 9

• appears to have a single axon
• most sensory neurons

Question 10

glial cells - astrocytes

Answer 10

• part of the CNS
• highly branched
• provide structural support
• regulate neuronal signalling
• contribute to blood-brain barrier
• help with neural tissue repair

Question 11

glial cells - ependymal cells

Answer 11

• part of the CNS
• epithelial-like
• line ventricles of brain and central canal of the spinal cord
• circulate cerebrospinal fluid (CSF)
• some form choroid plexuses, which produce CSF

Question 12

glial cells - microglia

Answer 12

• part of CNS
• small, mobile cells
• protect CNS from infection
• become phagocytic in response to inflammation

Question 13

glial cells - oligodendrocytes

Answer 13

• part of CNS
• cells with processes that can surround several axons
• cell processes form myelin sheaths around axons or enclose unmyelinated axons in the CNS

Question 14

glial cells - Schwann cells

Answer 14

• part of PNS
• single cells surrounding axons
• form myelin sheaths around axons or enclose unmyelinated axons in PNS

Question 15

glial cells - satellite cells

Answer 15

• part of PNS
• single cells surrounding cell bodies
• support neurons, providing nutrients
• protect neurons from heavy-metal poisons

Question 16

glial cells

Answer 16

supportive cells of the CNS and PNS - meaning they do not conduct action potentials
- carry out different activities that enhance neuron function and maintain normal conditions within nervous system
- most glial cells retain the ability to divide, whereas neurons do not

Question 17

myelin sheaths

Answer 17

specialized layers that wrap around the axons of some neurons
- formed by the cell processes of oligodendrocytes in the CNS and Schwann cells in the PNS by repeatedly wrapping around a segment of an axon to form a series of tightly wrapped cell membranes
- axons with these sheaths are called myelinated axons
- insulator that prevents almost all ion movement across the cell membrane
- gaps in sheaths are called nodes of Ranvier
- ion movements can occur at the nodes of Ranvier
- myelination increases the speed and efficient of action potential generation along the axon

Question 18

organization of nervous tissue

Answer 18

The nervous tissue varies in colour due to the location and arrangement of the parts of neurons and glial cells
1. gray matter:
- consists of groups of neuron cell bodies and their dendrites
- little myelin
- in CNS, gray matter on the surface of brain is called the cortex and clusters of grey matter located deeper within the brain are called nuclei
- in PNS, a cluster os neuron cell bodies is called ganglion
2. white matter:
- consist of bundles of parallel axons with their myelin sheaths, which are whitish coloured
- white matter of the CNS forms nerve tracts (conduction pathways) which propagate action potential from one area of the CNS to another
- white matter of PNS consist of bundles of axons and associated connective tissue that form nerves

Question 19

two basic types of ion channels

Answer 19

1. leak channels
   - always open
   - ions can “leak” across the membrane, down their concentration gradient
2. gated channels
   - closed until opened by specific signals
   - chemically gated channels are opened by specific or other chemicals
   - voltage gated channels are opened by a change in the electrical property of the cell membrane

Question 20

sides of the cell membrane

Answer 20

inside is usually negatively charged while outside is positively charged
- the uneven charge means that the membrane is polarised
- in an unstimulated (or resting) cell, we were to this as the resting membrane potential

Question 21

resting membrane potential

Answer 21

generated primarily by the uneven distribution of K+, Na+, and negatively charged proteins across the cell membrane
- higher concentration of K+ inside the cell and a higher concentration of Na+ outside the cell
- there are more negatively charged proteins inside the cell

Question 22

neuron communication

Answer 22

neuron cells, as well as muscle cells, are excitable cells meaning that the resting membrane potential changes in response to stimuli
- for muscle cells this change results in a contraction
- for neuron cells this change is a means of cell communication with other cells
3 stages of neuron communication:
1. generation of action potentials
2. action potentials propagation along the cell membrane
3. communication with target cell at the synapse

Question 23

action potential

Answer 23

electrical signals that are conducted along the cell membrane from one region of the cell to another
- channels responsible for action potentials are voltage-gated Na+ and K+ channels
- occur in an all or none fashion - if threshold is reached action potential WILL occur but if its not reached it won’t occur

Question 24

action potential steps

Answer 24

1. when the cell membrane is at rest, the voltage-gated channels are closed
2. when a stimulus occurs to a nerve cell, following neurotransmitter activation of chemically gated channels, Na+ channels open briefly (called local current), causing the inside of the cell membrane to become positive (called depolarisation). This depolarisation results in a local potential, but if the depolarisation isn’t strong enough, Na+ channels close again and local potential disappears w/out being conducted along the neuron cell membrane.
   If depolarisation is strong enough, Na+ enters the cell so that the local potential reaches a threshold value. This threshold depolarisation causes voltage-gated Na+ channels to open. Threshold is most often reached at the axon hillock, near the cell body. The opening of these channels causes a massive increase in membrane permeability to Na+ and voltage-gated K+ channels also begin to open. As more Na+ enters the neuron, depolarisation continues at a much faster pace. Eventually a brief reversal of charge takes place across the cell membrane (inside is positive relative to the outside)
3. the charge reversal causes Na+ channels to close and Na+ then stops entering the cell. more K+ channels are opening and K+ leaves the cell. The outward flow of K+ repolarises the cell membrane to its resting potential

Question 25

hyperpolarization

Answer 25

at the end of repolarisation the charge of the cell membrane briefly becomes more negative than the resting potential which is called hyperpolarization

Question 26

action potential conduction

Answer 26

occurs in two ways: 1. continuous conduction - occurs in unmyelinated axons - action potential stimulates local currents in adjacent parts of the cell membrane 2. saltatory conduction - occurs in myelinated axons - action potential at one node of Rainier causes a local current to flow through the surrounding extracellular fluid and through the cytoplasm of the axon to the next node, stimulating an action potential at that node of Ranvier - this conduction greatly increases the conduction velocity because of the nodes - action potentials are conducted slowly in unmyelinated axons and more rapidly in myelinated axons

Question 27

synapse

Answer 27

is a junction where the axon of one neuron interacts with another neuron or with cells of an effector organ (like muscle or glands) structure: 1. the end of the axon forms a presynaptic terminal 2. the membrane of the dendrite or effector cell is the postsynaptic membrane 3. the space separating the presynaptic and postsynaptic membranes is the synaptic clef - communication between the neuron and its target cell occurs through chemical signals by neurotransmitters - neurotransmitters are stored in synaptic vesicles in the presynaptic terminal - specific channel types and whether or not they open or close depend on the type of neurotransmitter in the presynaptic terminal and the type of receptor on the postsynaptic membrane, the response is either stimulation or inhibition of an action potential in the postsynaptic cell - neurotransmitters do not normally remain the synaptic cleft - they become reduced in concentration when they are either rapidly broken down by enzymes w/in the synaptic cleft or are transported back into the presynaptic terminal

Question 28

CNS neuronal pathways

Answer 28

1. converging pathways - two or more neurons synapse with the same postsynaptic neuron - this allows information transmitted in more than one neuronal pathway to converge into a single pathway 2. diverging pathways - the axon from one neuron divides and synapses with more than one other postsynaptic neuron - allows information transmitted in one neuronal pathway to diverge into two or more pathways Within the CNS (and many PNS) synapses, it takes more than a single action potential to have an effect

Question 29

summation

Answer 29

many presynaptic action potentials are needed in a process called summation - allows for integration of multiple sub threshold local potentials which can bring the membrane potential to threshold and trigger an action potential 1. spatial summation - occurs when the local potential originate from different locations on the postsynaptic neuron 2. temporal summation - occurs when local potentials overlap in time - both summation can lead to stimulation or inhibition depending on the type of signal

Question 30

spinal cord

Answer 30

extends from the foramen magnum at the base of the skull to the second lumbar vertebra - spinal nerves communicate between the spinal cord and the body - inferior end of the spinal cord and the spinal nerves exiting there is called the cauda equina - white matter in the spinal cord is organised into 3 columns: (1) dorsal (posterior) column (2) ventral (anterior) column (3) lateral column - each column contains ascending and descending tracts or pathways - ascending consists of axons that conduct action potentials toward the brain - descending consists of axons that conduct action potential away from the brain - gray matter of spinal cord is shaped like the letter H with dorsal horns and ventral horns - small lateral horns exist in levels of the spinal cord associated w the ANS - the central canal is a fluid-filled space in the centre of the spinal cord

Question 31

spinal nerves in spinal cord

Answer 31

spinal nerves arise from rootlets along the dorsal and ventral surfaces - the ventral rootlets combine to form a central root on the ventral side of the spinal cord - the dorsal rootlets combine to form a dorsal root on the dorsal side of the spinal cord at each segment - ventral and dorsal roots unite just lateral to the spinal cord to form a spinal nerve

Question 32

dorsal root ganglion

Answer 32

the dorsal root has a region called dorsal root ganglion - contains the cell bodies of pseudo-unipolar sensory neurons - the axons of these neurons originate in the periphery of the body - they pass through spinal nerves and the dorsal roots to the dorsal horn of the spinal cord gray matter - in the dorsal horn, the axons either synapse with interneurons or pass into the white matter and ascend or descend in the spinal cord

Question 33

ventral and lateral horns of spinal cord gray matter

Answer 33

contain the cell bodies of motor neurons, which regulate the activities of muscles and glands - somatic motor neurons are in the ventral horn, and autonomic neurons are in the lateral horn - axons from the motor neurons form the ventral roots and pass into the spinal nerves

Question 34

reflexes

Answer 34

involuntary reaction in response to a stimulus - allow for quicker response reflex arc is the neuronal pathway by which a reflex occurs - basic functional unit of the nervous - has 5 components: 1. a sensory receptor 2. a sensory neuron 3. in some reflexes, interneurons, which are neurons located between and communicating w two other neurons 4. a motor neuron 5. an effector organ (muscle or gland). the simplest reflex arcs do not involve interneurons. most reflexes occur in the spinal cord or brainstem rather than in the higher brain centres

Question 35

stretch reflex

Answer 35

occurs when muscles contract in response to a stretching force applied to them

Question 36

knee-jerk reflex or patellar reflex

Answer 36

1. when the patellar ligament is tapped, the quadriceps femoris muscle tendon and the muscles themselves are stretched. sensory receptors w/in these muscles are also stretched and the stretch reflex is activated 2. a sensory neuron monitoring the stretch receptor conducts action potentials to the spinal cord 3. sensory neurons synapse with motor neurons in the gray matter of the spinal cord segment. descending neurons w/in the spinal cord also synapse w the neurons of the stretch reflex, allowing for conscious modification to their activity 4. motor neuron from the spinal cord extend to the same muscle of the leg, stimulating them to contract, extending the leg, producing the characteristic knee-jerk response

Question 37

withdrawal reflex or flexor reflex

Answer 37

is to remove a limb or another body part from a painful stimulus 1. painful stimuli initiate action potential at the pain receptors 2. the sensory neurons monitoring these receptors conduct action potentials through the dorsal root to the spinal cord 3. the sensory neurons synapse with interneurons, which in turn synapse w motor neurons 4. these neurons stimulate muscles, usually flexor muscles, that remove the limb from the source of the painful stimulus

Question 38

4 major regions of the brain

Answer 38

1. brainstem 2. cerebellum 3. diencephalon 4. cerebrum

Question 39

brainstem

Answer 39

connects spinal cord to the brain 3 parts: 1. medulla oblongata 2. pons 3. midbrain - contains several nuclei involved in vital body functions like heart rate, blood pressure, and breathing - damage to these regions can cause death (but not for cerebrum or cerebellum)

Question 40

medulla oblongata

Answer 40

most inferior part of brainstem and is continuous w the spinal cord - contains ascending and descending nerve tracts to convey signals to and form other regions of the brain - contains discrete nuclei for regulation of heart rate and blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance, and coordination - on the anterior surface there are two enlargements called pyramids which consists of descending nerve tracts, which transmit action potentials from the brain to somatic motor neurons of the spinal cord and are involved in the conscious control of skeletal muscles

Question 41

pons

Answer 41

part of brainstem and are superior to the medulla oblongata - contains ascending and descending nerve tracts and several nuclei - some nuclei relay info between the cerebrum and the cerebellum - is the functional bridge between the cerebrum and the cerebellum - arched footbridge on the anterior surface - breathing, swallowing, and balance are also controlled in the lower pons - other nuclei in the pons control functions such as chewing and salivation

Question 42

midbrain

Answer 42

part of the brainstem, just superior to the pons and is the smallest region of the brainstem - dorsal part consists of 4 mounds of tissue called the colliculi - the two inferior colliculi are major relay centres for the auditory nerve pathways in the CNS - 2 superior colliculi are involved in visual reflexes and receive touch and auditory input - controls coordinating eye movement and controlling pupil diameter and lens shape - contains black nuclear mass called the substantial nigra which is part of the basal nuclei and regulates general body movements - the rest of the midbrain consists largely of ascending tracts from the spinal cord to the cerebrum and descending tracts from the cerebrum to the spinal cord or cerebellum

Question 43

reticular formation

Answer 43

scattered throughout the brainstem and is a group of nuclei - regulates cyclical motor functions, like respiration, walking, chewing - major component of activating system which plays an important role in arousing and maintaining consciousness and in regulating the sleep-wake cycle - general aesthetic suppress the reticular activating system - damage to cells of the reticular formation can cause coma

Question 44

cerebellum

Answer 44

attached to the brainstem by several large connections called cerebellar peduncles - the connections provide routes of communication between the cerebellum and other parts of the CNS

Question 45

diencephalon

Answer 45

is the part of the brain between the brainstem and the cerebrum contains: 1. thalamus - largest part and consists of a cluster nuclei and two large lateral parts connected in the centre by a small interthalamic adhesion - sensory input that ascends through the spinal cord and brainstem projects to the thalamus - influences mood and registers an unlocalised, uncomfortable perception of pain 2. epithalamus - small area superior and posterior to the thalamus - consists of small nuclei that is involved in the emotional and visceral response to doors, and the pineal gland - pineal gland is an endocrine gland that may influence the onset of puberty and plays a role in controlling some long-term cycles that are influenced by the light-dark cycle 3. hypothalamus - most inferior part and contains small nuclei that maintains homeostasis - plays a central role in body temp, hunger, thirst, sexual pleasure, rage, fear, and relaxation after a meal - infundibulum extends from the floor of the hypothalamus to the pituitary gland - controls the secretion of hormones from the pituitary gland - mammillary bodies form externally visible swelling on the posterior portion and are involved in emotional responses to odors and in memory

Question 46

cerebrum

Answer 46

largest part of the brain - divided into 2 hemispheres by a longitudinal fissure - gyri greatly increase the surface area of the cerebral cortex - intervening grooves are called sulci Each cerebral hemisphere is divided into lobes: 1. frontal lobe 2. parietal lobe 3. occipital lobe 4. temporal lobe

Question 47

frontal lobe

Answer 47

voluntary motor functions, motivation, aggression, mood, and olfactory (smell) reception

Question 48

parietal lobe

Answer 48

receiving and consciously perceiving most sensory info, such as pain, touch, temp, and balance. - frontal and parietal lobes are separated by the central sulcus

Question 49

occipital lobe

Answer 49

functions in receiving and perceiving visual input and is not distinctly separate from the other lobes

Question 50

temporal lobes

Answer 50

involved in olfactory (smell) and auditory sensations - important for memory - anterior and inferior portions called psychic cortex and associated w abstract though and judgment - most of temporal lobe is separated from the rest of the cerebrum by the lateral fissure

Question 51

insula

Answer 51

deep within the lateral fissure (sometimes called the 5th lobe) and is involved in the perception of taste

Question 52

spinothalamic

Answer 52

ascending tract function: pain, temp, light touch, pressure, tickle and itch sensations

Question 53

ascending tract

Answer 53

spinal cord and brainstem contain a number of ascending tracts that transmit info via action potential from ht periphery to various parts of the brain - each tract is involved with a limited type of sensory input, such as pain, temp, touch, position, or pressure - each tract contains axons from specific sensory receptors specialised to detect a particular type of stimulus - consists of 2 or 3 neurons from the periphery to the brain - left side of the brain received sensory input from the right side of the body (vice versa) - ascending tract terminate in the brainstem or cerebellum

Question 54

dorsal column

Answer 54

ascending tract function: proprioception, deep pressure, and vibration

Question 55

spinocerebellar (anterior and posterior)

Answer 55

ascending tract function: proprioception to cerebellum

Question 56

sensory areas of the cerebral cortex

Answer 56

- ascending tracts project specific regions of the cerebral cortex called primary sensory areas where sensations are perceived - primary somatosensory cortex (general sensory area) is located in the parietal lobe posterior to the central sulcus - sensory fibres carrying general sensory input (pain, pressure, temp) synapse in the thalamus, and thalamic neurons relay the info to the primary somatosensory cortex - cortical areas immediately adjacent to the primary sensory areas called association areas are involved in the process of recognition

Question 57

voluntary movements

Answer 57

result from the stimulation of neural circuits that consist of two motor neurons: 1. upper motor neurons - have cell bodies in the cerebral cortex - the axons on this neuron form descending tracts that connect to lower motor neurons 2. lower motor neurons - have cell bodies in the ventral (anterior) horn of the spinal cord gray matter or in cranial nerve nuclei - axons leave the CNS and extend through spinal or cranial nerves to skeletal muscles

Question 58

primary motor cortex

Answer 58

is located in the posterior portion of the frontal love - action potentials initiated in this region control voluntary movements of skeletal muscles

Question 59

premotor area

Answer 59

the premotor area of the frontal lobe is where motor functions are organised before they are actually initiated in the primary motor cortex

Question 60

prefrontal area

Answer 60

the motivation and foresight to plan and initiate movement occurs in the anterior portion of the frontal lobe, the prefrontal area - involved in motivation and regulation of emotional behaviour and mood

Question 61

basal nuclei

Answer 61

is a group of functionally related nuclei - two primary: corpus striatum (located deep w/in the cerbrum), substantia nigra (a group of darkly pigmented cells in midbrain - important in planning, organising, and coordinating motor movements and posture

Question 62

cerebellum (more in-depth)

Answer 62

attached by cerebellar peduncles to the brainstem - cerebellar cortex is composed of gray matter and has gyri and sulci - internally the cerebellum contains gray nuclei and white nerve tracts - involved in maintaining balance and muscle tone and in coordinating fine motor movements - if damaged you become clumsy and muscle tone decreases - major function is comparator: a sensing device that compares the data from 2 sources

Question 63

Autonomic nervous system (ANS)

Answer 63

comprises motor neurons that carry action potentials from the CNS to the periphery - innervate smooth muscle, cardiac muscle, and glands - largely controlled unconsciously 2 neurons extend from the CNS to the effector organ: 1. preganglionic neuron 2. postganglionic neuron division: Sympathetic - prepares individual for physical activity - fight or flight Parasympathetic - rest and digest - stimulates involuntary activities of the body at rest

Question 64

anatomy of the sympathetic division

Question 65

anatomy of the parasympathetic divison

Question 66

autonomic neurotransmitters

Answer 66

acetylcholine - secreted by all preganglionic neurons from both sympathetic and parasympathetic division norepinephrine - secreted by most postganglionic neurons of the sympathetic division

Question 67

function so the autonomic nervous system

Answer 67

most found in mod 4 notes but may be some more important info in this chapter