OC1 - nervous system

Question 1

what are the components of a neuron?

Answer 1

dendrite, cell body, nucleus, axon, myelin sheath, schwann cell, nodes of ranvier, axon terminal

Question 2

what are the two main divisions of the nervous system?

Answer 2

central
peripheral

Question 3

what are the components of the central nervous system?

Answer 3

brain
spinal cord

Question 4

what are the divisions of the peripheral nervous system?

Answer 4

motor neurons - somatic and autonomic
sensory neurons
spinal nerves, cranial nerves, and ganglia

Question 5

what are the divisions of the autonomic nervous system?

Answer 5

sympathetic
parasympathetic

Question 6

what is the somatic nervous system?

Answer 6

under voluntary control
innervates skeletal muscle
motor neuron is one continuous structure

Question 7

what is the autonomic nervous system?

Answer 7

sympathetic and parasympathetic
under involuntary control
innervates cardiac muscle, smooth muscle, and glands
two motor neurons - one pre-ganglionic and one post-ganglionic

Question 8

what is the sympathetic nervous system?

Answer 8

‘fight or flight’
controls function in times of stress
short pre-ganglionic neuron
long post-ganglionic neuron
adrenergic neurotransmitters - e.g. adrenaline, long lasting effect

Question 9

what are the roles of the sympathetic nervous system?

Answer 9

dilates pupils
increases heart rate
inhibits saliva production
relaxes urinary bladder

Question 10

what is the parasympathetic nervous system?

Answer 10

‘rest and digest’
controls day to day function
long pre-ganglionic neuron
short post-ganglionic neuron
cholinergic neurotransmitters - e.g. acetylcholine, effects are brief as they are inactivated quickly in the synaptic cleft.

Question 11

what are the roles of the parasympathetic nervous system?

Answer 11

constricts pupils
decreases heart rate
increases saliva production
constricts urinary bladder

Question 12

what is a reflex?

Answer 12

a quick involuntary response to a change in the internal or external environments

Question 13

what is a somatic reflex?

Answer 13

uses somatic motor neurons that excite skeletal muscle cells.
e.g. stretch reflex (knee jerk), tendon reflex, flexor reflex, crossed extensor reflex

Question 14

what is a visceral (autonomic) reflex?

Answer 14

involves visceral organs and uses autonomic motor neurons to control cardiac or smooth muscle cells.
e.g. gastric reflex, pupillary reflex, propriocepetion

Question 15

what are the components of a reflex arc?

Answer 15

1. receptor
2. sensory neuron
3. relay neuron
4. motor neuron
5. effector

Question 16

what is the function of the ‘receptor’ in a reflex arc?

Answer 16

detects changes in the internal or external environment and triggers a nerve impulse

Question 17

what is the function of the ‘sensory neuron’ in a reflex arc?

Answer 17

carries signals from sensory receptors to the central nervous system

Question 18

what is the function of the ‘relay neuron’ in a reflex arc?

Answer 18

carries signals from one part of the nervous system to another

Question 19

what is the function of the ‘motor neuron’ in a reflex arc?

Answer 19

initiates response to stimuli, carries signals from the central nervous system to an effector.

Question 20

what is the function of the ‘effector’ in a reflex arc?

Answer 20

muscle or gland
responds to nerve impulse

Question 21

what are the types of reflex arc?

Answer 21

monosynaptic
polysynaptic
ipsilateral
contralateral
intersegmental
reciprocal innervation

Question 22

what is a monosynaptic reflex arc?

Answer 22

a pathway with only one synapse in the central nervous system

Question 23

what is a polysynaptic reflex arc?

Answer 23

a pathway with more than two types of neuron and more than one central nervous system synapse.

Question 24

what is an Ipsilateral reflex arc?

Answer 24

sensory input and motor output are on the same side of the spinal cord
e.g. knee jerk reflex or flexor reflex

Question 25

what is a contralateral reflex arc?

Answer 25

sensory input and motor output are on opposite sides of the spinal cord e.g. crossed extensor reflex

Question 26

what is an intersegmental reflex arc?

Answer 26

sensory impulses from one neuron go up and down the spinal cord and activate association neurons in different segments of the spinal cord e.g. flexor reflex

Question 27

what is a reciprocal innervation reflex arc?

Answer 27

acts on antagonistic pairs of muscles causing simultaaneous contraction of one muscle and inhibition of contraction of its antagonistic pair e.g. flexor reflex

Question 28

describe the generation of an action potential (full answer)

Answer 28

resting membrane potential is -70mV. neurotransmitter is released from the pre-synaptic neuron via exocytosis due to the presence of calcium ions. neurotransmitter binds to receptors on the post-synaptic membrane so Na+ ions enter the cell increasing the membrane potential, once threshold potential -55mv is reached all Na+ channels open causing a large influx of Na+ ions into the cell leading to membrane depolarisation and the generation of an action potential +30mV, following this there is a refractory period where there is a slow opening of K+ channels to restore the resting potential, -70mV, and the neurotransmitter is broken down in the synaptic cleft.