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ansc 3080 > neurophysiology > Flashcards

neurophysiology Flashcards

1
Q

what are the two main categories of the nervous system and what do they contain?

A

central nervous system: brain and spinal cord
peripheral nervous system: the rest of the nerves

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2
Q

what is the PNS divided into and what are their functions?

A

sensory system: sensory/afferent neurons carry information from PNS to CNS
somatic motor system: motor/efferent neurons carry out action after integration withing CNS, voluntary skeletalmuscle movements (except shivering and reflexes)
autonomic system: involuntary motor nerves that control smooth muscle

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3
Q

what is the autonomic system divided into and what are their functions?

A

sympathetic NS: fight or flight system, control of stress response
parasympathetic NS: rest and digest, homeostasis

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4
Q

what are neurons and what are they composed of?

A

nerve cells that transmit info, composed of a cell body, axons, and dendrites

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5
Q

what do axons and dendrites do?

A
  • axons transmit info away from the soma/cell body
  • dendrites receive info and pass it on to the soma which integrates it
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6
Q

how are neurons categorized and what are the three categories and their functions?

A

categorized based on number of processes
- multipolar: associated with CNS, motor/efferent neurons
- pseudounipolar: associated with PNS, sensory/afferent neurons
- bipolar: involved in sensory organs, interneurons that relay info from PNS to CNS or between neurons within CNS

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7
Q

what are glial cells?

A

non neuronal cells that support neurons with structure and nutrition and form the myelin sheath by wrapping around an axon

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8
Q

what is white matter?

A

myelinated neurons, corresponds to bundles of neuron processes, processes info

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9
Q

what is grey matter?

A

cell bodies, unmyelinated, integrates info

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10
Q

what are ganglia?

A

clusters of sensory neuron cell bodies outside CNS

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11
Q

what is a resting membrane potential and how is it maintained?

A
  • the difference in potential across a cell where the inside is negative relative to the outside
  • maintained by selective permeability/passive diffusion, sodium-potassium pump, large anions inside the membrane
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12
Q

what is diffusion?

A

passive leakage of ions through channels down a conc. gradient, permeable to K+ and not so much to other ions

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13
Q

how does the sodium-potassium pump work?

A

pumps 3 Na+ out and 2 K+ in to compensate for diffusion leakage, goes against the conc. gradient so it requires energy

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14
Q

what is an excitable cell?

A

cell that generates electrical impulses in response to a certain level of stimulus that induces a change in membrane potential

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15
Q

how can excitable cells become excited?

A

chemical, electrical, or physical stimulus induces a change in membrane potential to reach a threshold, which causes the opening of voltage gated ion channels

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16
Q

what happens when voltage gated ion channels open?

A

depolarization, where ions rush inside the cell down their conc. gradients which results in a less negative membrane potential which eventually becomes positive

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17
Q

what is repolarization?

A

opening of K+ channels that results in outflow of K+, returning to RMP

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18
Q

what is hyperpolarization?

A

K+ outflow continues after RMP is reached so it becomes more negative, this is due to the K+ channel taking a longer time to close

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19
Q

what is the refractory period?

A

neurons can’t be restimulated until RMP is restored

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20
Q

what is the all or nothing rule?

A

stimulus must reach the threshold in order to generate an AP which is defined by the number of voltage gated channels in a neuron

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21
Q

what determines the strength of a signal?

A

number of APs generated per second (frequency)

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22
Q

what are ion gated channels?

A

channels opened by specific ligands instead of electrical stimuli, various degrees of specificity

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23
Q

what is saltatory conduction?

A

myelin prevents ion leakage, current jumps from one node to the other

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24
Q

what is required of neurons before they can conduct APs?

A

they must be precisely spaced

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25
Q

what does the velocity of the signal depend on?

A

thickenss of the myelin and diameter of fibre, thicker fibre = faster signal

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26
Q

what is synaptic transmission?

A

continuity of signal between neurons or between neuron and target cell

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27
Q

what are neurotransmitters and what types are there?

A
  • molecules able to transmit info from a neuron to convert the electrical signals into a chemical signal, they jump at the synaptic cleft
  • small molecules: synthesized in cell body, packaged in secretory vesicles, and transported to site of release
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28
Q

what is the general method of action of a neuromuscular synapse?

A
  1. AP is generated
  2. voltage gated Ca2+ channels open, Ca2+ rushes in
  3. Ca2+ triggers exocytosis of neurotransmitter (ACh)
  4. ACh diffuses into the cleft
  5. ACh binds to receptors
  6. ion channels open on postsynaptic membrane (depolarization)
  7. neurotransmitter inactivated, signal terminated
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29
Q

what are the different ion channels and where are they located?

A
  • Na+ for neurons
  • Ca2+ for certain nerve endings, smooth, and cardiac muscle
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30
Q

how can surface area be increased in neuromuscular synapses?

A

postsynaptic folding

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31
Q

how is transmission terminated in different neurotransmitters?

A
  • small molecules: neurotransmitters reabsorbed by presynaptic neuron via endocytosis, recycled for further use, or deactivated in cleft by enzymes from postsynaptic neuron
  • neuropeptides: after receptor binding, can be internalized by post synaptic cell via endocytosis and degraded by enzymes or broken down by peptidase in the gap
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32
Q

how many APs are generated in each synapse?

A
  • neuromuscular synapse: 1 neuron can only generate 1 AP at a time
  • neuron-neuron synapse: 1 neuron can receive AP from multiple other neurons due to multiple dendrites and synapses may be excitatory or inhibitory
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33
Q

what are excitatory and inhibitory synapses?

A
  • excitatory: depolarization and entry of Na+ into cell
  • inhibitory: hyperpolarization, entry of Cl-/outflow of K+ which prevents AP transmission
34
Q

what is the brain composed of and what does each component include?

A

cerebrum (forebrain)
- diencephalon (thalamus, hypothalamus)
- cerebellum
- brain stem (mesencephalon, pons, medulla oblongata)

35
Q

how many layers is the brain composed of and what are their functions?

A

three layers
- deepest: controls critical body functions
- middle: secondary functions
- superficial: thinking and problem solving

36
Q

what is the task of the CNS?

A

receive, process, send info to effectors

37
Q

what are the meninges ans what are their functions?

A

3 membranous layers surrounding the brain and spinal cord
- dura mater: outer layer, thick, supports the brain, inserted between cerebral hemispheres and forms venous sinus which collects most of the blood and CSF from the brain
- arachnoid: middle layer, forms subarachnoid space with inner membrane which is filled with cerebrospinal fluid
- pia mater: inner layer, tightly attached to neural tissue to form blood brain barrier

38
Q

what is cerebrospinal fluid?

A

fluid with that circulates around the brain and spinal cord, provides nutrients and shock absorption to CNS, maintains blood-CSF barrier and ionic concentrations

39
Q

what is the path of cerebrospinal fluid?

A

diffuses from 4th ventricle to subarachnoid space and circulates around brain and spinal chord, then drains from subarachnoid space through arachnoid villi into venous sinus before entering blood circulation

40
Q

how does hydrocephaly occur?

A

dysfunctional arachnoid villi can’t drain CSF so it swells and causes skull deformities

41
Q

what is the blood brain barrier?

A

barrier that prevents cells, proteins, amino acids and only lipid soluble substances like gases can diffuse through the barrier

42
Q

what is the cerebrum?

A

part of the brain responsible for higher thought and conscious decision making, separated into two areas: cerebreal and neocortex

43
Q

what is the cerebral cortex?

A

grey matter, most superficial layer of cerebrum, convoluted, conscious experience of sensory input, high degree of educability (can learn a different response to a stimulus)

44
Q

what is the neocortex?

A

most complex part of cerebrum

45
Q

what are association cortices?

A

cortices that are not assigned a specific role but connect areas with defined reactions

46
Q

what is basal nuclei?

A

paired nuclei composed of large pools of neurons deep within the cerebrum close to the thalamus; they control complex semivoluntary movements like locomotion and work in conjunction with the cortex and cerebellum

47
Q

what is the cerebellum and how does it receive information?

A
  • responsible for control of smooth motion through corrective signals sent via thalamus to the cortex and spinal nuclei so if it’s damaged, intended movement would be distorted, it’s well developed in animals that require precise adjustments
  • inner ear for balance, proprioceptive receptors for muscles, tendons, and joints, cortex for visual and motor
48
Q

what is the diencephalon and what does it contain?

A

interbrain, contains the thalamus, epithalamus, and hypothalamus

49
Q

what is the thalamus?

A

relay station for sensory info, cerebellum and basal ganglia, and cerebral cortex

50
Q

what is the epithalamus?

A

contains olfactory correlation centre and pineal gland

51
Q

what is the hypothalamus?

A

produces neuropeptides that control the anterior pituitary, neurohormones released by posterior pituitary, principle regulator of autonomic NS

52
Q

what are the most important regions for homeostasis?

A

hypothalamus and brainstem

53
Q

what is the brain stem and what does it contain?

A

includes nuclei that govern body function by reflexes, large amounts of white matter, and 3 regions: mesencephalon, pons, medulla oblongata

54
Q

what is the mesencephalon and which animals have it well developed?

A
  • visual reflex centre, receives visual info and controls eye movement paired with auditory reflex centre
  • very well developed in birds, most mammals have small midbrains
55
Q

what is the pons?

A

contains center for postural reflexes and control of respiratory movements

56
Q

what is the medulla oblongata?

A

crucial for control of heart activity, blood pressure, and relative distribution of organs

57
Q

how many pairs of cranial nerves are there?

A

12

58
Q

which cranial nerves are purely sensory and where are they?

A
  • 1 (olfactory) and 2 (optic)
  • remain in the brain
59
Q

what is the spinal cord and what does it contain?

A
  • grey matter surrounded by white matter, conveys information
  • grey matter: cell bodies and dendrites
  • dorsal horn: carries sensory info
  • ventral horn: carries motor and autonomic info
  • spinal nerves: entry and exit of neurons from spinal cord, formed by joined ventral and dorsal roots which merge within the spinal cord
60
Q

what does each spinal segment do?

A

receive sensory info from skin and sends info to muscles and this can predict the effects of spinal cord injury

61
Q

what may be the cause of an animal having no withdrawal response?

A

issue with spinal cord; no processing of sensory information therefore no motor response

62
Q

what are the 3 levels of control for the CNS?

A
  • higher centres: cerebral cortex (conscious)
  • middle centres: sensorimotor cortex, cerebellum (monitors smooth movement execution)
  • lower level: spinal cord from which motor neurons exit (somatic reflex arcs)
63
Q

what sends sensory info back to CNS?

A

tensions in muscles and tendons and angles of joints (proprioception)

64
Q

what is a reflex?

A

involuntary and unvarying response of effector organs to a stimulus

65
Q

what are the 5 fundamental components of a reflex?

A
  • sensory cells
  • sensory nerve fibres
  • coordinating centre (CNS)
  • motor nerve fibres
  • effectors
66
Q

what are receptors?

A

trasnsmit environmental info like temp and pressure, stretch, tension, and convert that info into APs, frequency enables CNS to detect intensity

67
Q

what are sensory nerves?

A

afferent, conduct AP from receptor, cell body in ganglion outside of spinal cord, fibres entering spinal cord via dorsal roots

68
Q

what is a coordinating centre?

A

monosynaptic (muscle spindle reflex) or multisynaptic (elaborate reflexes)

69
Q

what is a motor nerve?

A

efferent, carries APs from CNS to target organs via ventral roots, cell body within CNS

70
Q

what are muscle spindles and how do they work?

A
  • aka intrafusal fibres, modified muscles fibres that act as stretch receptors to detect changes in muscle length
  • when muscle lengthens, it tightens around synapse and pinches the nerve to signal stretching of the muscle, the signal is sent by a sensory nerve to the motor neurons serving the same muscle, muscle shortens
71
Q

what typical reflex component is missing from the stretch receptor arc?

A

integration centre; the sensory nerve directly contacts the motor nerve bc no higher processing is needed for stretch stimuli

72
Q

what is the method of action for a change in tendon length?

A
  1. muscle contracts
  2. pulls tendon
  3. changes detected by golgi organ, squeezes bare end of neuron (receptors)
  4. sensory nerve contacts inhibitory interneuron in spinal cord
  5. inhibits motor neurons serving same muscle
73
Q

what is the knee jerk reflex?

A

quadriceps muscle contraction in response to tapping of the patella ligament, causes brief leg extension, requires relaxation of opposing flexor muscles via activation of inhibitory interneurons

74
Q

what loop does the ANS function with?

A

negative feedback

75
Q

what are the control centres of the ANS and what are their functions?

A
  • hypothalamus (master command)
  • brain stem (respiratory centre)
  • spinal cord (local integration in thoracic and sacral regions)
76
Q

how do motor nerve fibres work in the ANS?

A

target organs are smooth muscle, cardiac muscle, and glands, signal goes through other nerves instead of directly to the effector

77
Q

what is a preganglionic neuron?

A
  • neuron that travels from the thoracolumbar spinal cord to the sympathetic ganglia where they synapse with postganglionic neurons (acetylcholine)
  • forms a chain parallel to the spinal cord, may extend to the adrenal medulla to stimulate secretion of epinephrin and norepinephrine into blood circulation
78
Q

what is a postganglionic neuron?

A
  • neuron that travels from the ganglion to target organs (norepinephrine/ACh)
79
Q

how do the ganglionic neurons work when the sympathetic NS activates?

A

outflow from thoracolumbar spinal cord, preganglionic axons enter paravertebral sympathetic ganglion chain (info is shared between ganglia along the chain), synapse with post ganglionic nerves along the chain which send signals to target organs

80
Q

what are the two receptors for ACh and how do they differ?

A
  • nicotinic receptors: at the postganglionic neuron in the sympathetic NS and neuromuscular junctions, ionotropic (Na+ gated channel)
  • muscarinic: at the effector inthe parasympathetic NS, separate from ion channel, require intracellular secondary messengers to activate target cell, can be stimulatory or inhibitory, slower and more prolonged effect
81
Q

what are characteristics of the parasympathetic NS?

A
  • activates during rest to maintain homeostasis
  • preganglionic neurons originate in brain/sacral spinal cord
  • axons travel to ganglia near effector regions
  • no sharing of info within preganglionic fibres
  • short axons on postganglionic fibres that connect directly to specific organs (no branching, no hormones)
  • selective action

ansc 3080 (3 decks)

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