week 3

Question 1

3 basic functions of NS

Answer 1

sensory - integrative - motor

Question 2

general sensory receptors

Answer 2

• sensory input
  Located: skin, skeletal muscles, tendons, joints and visceral organs
• thermoreceptors, nociceptors, mechanoreceptors (tactile, baro, proprioceptors)

Question 3

special sensory receptors

Answer 3

• located eye, ears, mouth and nose
• photoreceptors - chemoreceptors - mechanoreceptors (hair cells)

Question 4

peripheral NS

Answer 4

• sensory receptors and the cranial, spinal and peripheral nerves that link all parts of the body to the CNS
• cranial (head and neck) and spinal nerves (all body)

Question 5

2 functional divisions: PNS

Answer 5

sensory division (affarent)

motor division (efferent)

Question 6

somatic NS

Answer 6

conveys somatic motor output from the CNS to bodies skeletal muscles
- control voluntary skeletal movements and involuntary skeletal muscle movements = somatic reflexes

Question 7

autonomic NS

Answer 7

conveys autonomic motor output from the CNS to bodies cardiac and smooth muscles
- involuntary activities; heart rate, respiration, pupil diameter, blood vessel diameter, digestion of food, urination, defecation and salivation

Question 8

ANS: sympathetic division

Answer 8

• controls fight or flight activities
• activates body functions that support physical activities
• increases HR, respiratory airflow, blood flow to skeletal muscles and sweat glands, dilates pupils, digestive functions, inhibits urination and deification

Question 9

ANS: parasympathetic NS

Answer 9

controls rest and digest activities - activates body functions that converse and restore body energy
- stimulates digestive functions, urination and deification, decreases heart rate and airflow

Question 10

dendrites

Answer 10

main receptive (input) region of a neuron
- sensory receptors - detects stimuli - receives info from other neurons

Question 11

cell body

Answer 11

receives information from other neurons and converts this into graded potential - integrates information and conveys info towards towards to the initial segment of the axon

Question 12

axon

Answer 12

generates and conducts action potentials to convey the information from the initial segment to the axon terminals

Question 13

myelin sheath

Answer 13

protects and insulates the axon terminal
- increases the speed of signal conduction

Question 14

axon terminals

Answer 14

forms a synapse with another cell
- secretory region contains synaptic vesicles that store and release neurotransmitters

Question 15

nuclei (nucleus)

Answer 15

clusters of neuron cell bodies in CNS

Question 16

ganglia (ganglion)

Answer 16

clusters of neuron cell bodies in PNS

Question 17

tracts

Answer 17

bundles of neuron axons in CNS

Question 18

nerves

Answer 18

neuron axons bundled in PNS

Question 19

sensory neurons

Answer 19

• conduct sensory input from receptors to CNS
• unipolar in structure

Question 20

interneurons

Answer 20

• conduct information within the CNS
• multipolar in structure

Question 21

motor neurons

Answer 21

• conduct motor output away from the CNS to a muscle or gland
• lower motor neurons: somatic motor output
• pre and postganglionic neurons: autonomic motor output
• multipolar in structure

Question 22

chemically gated channels

Answer 22

stimulus- open in response to chemical stimulus
located- dendrites and cell body

Question 23

mechanically gated channels

Answer 23

open in response to mechanical stimulation (touch, vibration, pressure)
located- along plasma membrane of dendrites

Question 24

voltage-gated channels

Answer 24

open and close in response to voltage gated changes (membrane potential)

Question 25

depolarisation

Answer 25

- an influx of Na+ ions into ICF - ICF gains more positive ions - membrane potential becomes LESS negative - -70mv to -60mv

Question 26

hyperpolarisation

Answer 26

- efflux of K+ ions out of ICF - ICF loses positive ions - membrane potential becomes MORE negative - -70 t0 -90mv

Question 27

graded potential : generated

Answer 27

a small change in the membrane potential (small depolarisation or hyperpolarisation)

Question 28

graded potential : conducted

Answer 28

originates in the dendrites or cell body of the neuron, when a stimulus opens chemically gated (dendrites and cell body) or mechanically gated channels (dendrites) - short distance signal

Question 29

action potential : generated

Answer 29

depolarisation - repolarisation - hyperpolarisation - threshold

Question 30

action potential : conducted

Answer 30

originates at the initial segment of an axon - long distance signal - involve voltage-gated channels - self propagating

Question 31

continuous conduction

Answer 31

- occurs in unmyelinated axons - action potentials are generated at the voltage-gated channels along the length of an axon - conduction occurs at speeds <2m/s

Question 32

saltatory conduction

Answer 32

- occurs in myelinated axons - action potentials are generated at the nodes of Ranvier - conduction occurs at speeds of >100m/s

Question 33

local anaesthetics impairing action potential

Answer 33

- block voltage-gated Na+ channels - no action potential - no sensation of pain - no conduction of pain signal to brain

Question 34

ice packs + pressure impairing action potential

Answer 34

impairs signal conduction by restricting blood flow - reduced pain sensation

Question 35

step 1 information transfer

Answer 35

action potential arrives at and depolarises the axon terminal

Question 36

step 2 information transfer

Answer 36

depolarisation of the axon terminal stimulates voltage-gated calcium channels to open and calcium enters the axon terminal

Question 37

step 3 information transfer

Answer 37

calcium entry triggers synaptic vesicles to release stored neurotransmitters into the synaptic cleft

Question 38

step 4 information transfer

Answer 38

neurotransmitters diffuse across the synaptic cleft and bind to chemically gated channels (on postsynaptic membrane dendrites or cell body)

Question 39

step 5 information transfer

Answer 39

binding of neurotransmitters opens chemically gated channels - an influx of sodium into the ICF - plasma membrane of postsynaptic neuron depolarises - graded potential known as excitatory postsynaptic potential is produced

Question 40

step 6 information transfer

Answer 40

EPSP travels to and depolarises initial segment of the postsynaptic neuron to the threshold (-55mv) - action potential generated - information successfully transmitted

Question 41

reuptake

Answer 41

when a neurotransmitter diffuses away from the synaptic cleft - is degraded by enzymes - re-enters the axon terminal and is destroyed by enzymes or reused

Question 42

step 1 neural transmission - across neuron

Answer 42

- stimulus (touch, pain, neurotransmitter) opens chemically or mechanically gated Na+ channels of the dendrites (or cell body) - sodium enters ICF - membrane potential depolarises - graded potential produced

Question 43

step 2 neural transmission - across neuron

Answer 43

- if graded potential travels to the initial segment of the axon and depolarises the membrane potential to threshold - voltage-gated Na+ channels open - Na+ enters the ICF - action potential generated

Question 44

step 3 neural transmission - across neuron

Answer 44

AP generated at the initial segment triggers the generation of another AP in the adjacent region (2nd AP triggers 3rd AP and so on)

Question 45

step 4 neural transmission - across neuron

Answer 45

the AP arriving at the axon terminals triggers the presynaptic neuron to release a neurotransmitter which carries the signal to a post synaptic cell (neuron, muscle or gland)