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Human bio > Nervous system > Flashcards

Nervous system Flashcards

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Biology 101 flashcards
1
Q

explain the conduction of a nerve impulse along myelinated fibres

A
  1. depolarisation occurs
  2. saltatory conduction at nodes of Ranvier
  3. cell membrane becomes permeable to sodium ions
  4. needs to reach theshold (-55mV)
  5. sodium ions inter the cell
  6. membrane becomes positive to outside
  7. potassium ions diffuse out
  8. hyperpolarisation
  9. sodium-potassium pump acts: sodium out and potassium in
  10. membrane returns to polarised state
  11. action potential triggers depolarsiation in adjacent membrane regions
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2
Q

explain the transmission of a nerve impulse across a synapse

A
  1. When action potential reaches the axon terminals it triggers calcium gates, causing calcium to flood into the axon terminal
  2. The calcium binds with vesicles containing neurotransmitters and allows them to move to the cell membrane, releasing the neurotransmitter into the synaptic cleft
  3. These neurotransmitters diffuse across the synaptic cleft and attach to receptors on the membrane of the next neuron (dendrites/post-synaptic membrane)
  4. Results in the initiation of an action potential in the post-synaptic neuron (sodium gates open into the dendrites)
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3
Q

how do neurotransmitters go away after transmission across a synapse

A

Diffusion

Re-uptake (back into the axon terminal to be used again)

Broken down

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4
Q

how is the nervous system protected

A

bone

meninges

cerebrospinal fluid

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5
Q

explain how bone protects the nervous system

A

Cranium protects brain, vertebral column protects spinal cord

Protects from physical injury

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6
Q

explain how meninges protects the nervous system

A

Holds brain and spinal cord in place, carry blood vessels to the brain

Inner layer: dura mater

  • tough and fibrous
  • sticks closely to cranium/vertebral canal
  • anchors CNS to bone

Middle layer: arachnoid mater

  • loose mesh of fibres
  • connects with inner layer

Outer layer: pia mater is delicate

  • contains many blood vessels
  • sticks closely to the surface of brain and spinal cord
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7
Q

explain how cerebrospinal fluid protects the nervous system

A

Supports brain, gives it a medium to float in

shock absorber - protects from mechanical injury

Occupies space between meningeal layers

Circulates through 4 cavities in the brain and centre of spinal cord

Clear watery fluid containing cells, glucose, proteins, urea and salts

Formed from blood, circulates through CNS and takes nutrients to neurons and removes wastes and eventually returns to capillaries

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8
Q

give examples of neurotransmitters

A

acetylcholine

adrenaline

dopamine

histamine

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9
Q

list other functions of the cerebrospinal fluid

A

Shock absorber, protects from mechanical injury

Delivers nutrients to cells of CNS

Removes wastes

Regulates concentration of H+ and CO2, which regulates breathing

Maintains fluid to bathe cells of the brain

Transport chemical messengers around CNS

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10
Q

what are the 2 parts to the cerebrum

A

cerebral cortex

basal ganglia

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11
Q

describe the structure of the cerebral cortex

A

outer surface of cerebrum, grey matter - 2-4mm thick

folded - rounded ridges called convolutions, shallow downfolds calls sulci, deep downfolds called fissures

longitudinal fissures separate cerebral cortex into 2 cerebral hemispheres

hemispheres have four lobes: frontal, parietal, temporal, occipital

joining the hemispheres at the base of the longitudinal fissure is the corpus callosum (area of white matter)

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12
Q

what is the function of the cerebral cortex

A

involved in thinking, reasoning, learning, memory, intelligence, sense and responsibility

3 basic functions:
sensory areas: interpret impulses

motor areas: control muscular movement

association areas: intellectual and emotional processing

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13
Q

explain the structure of the basal ganglia

A

grey matter below cerebral cortex

composed of tracts - bundles of nerve fibres

mostly unmyelinated axons

outside of CNS

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14
Q

what is the function(s) of the basal ganglia

A

regulates muscle tone

integrates complex muscles actions in complicated, learned ways (e.g. walking)

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15
Q

what is the function of the cerebellum

A

takes place below conscious

receives information from inner ear and stretch receptors in skeletal cells

controls posture, balance and fine coordination of voluntary muscles

damaged cerebellum - jerky, uncontrolled movement

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16
Q

describe the structure of the cerebellum

A

2 hemispheres

surface is folded into parallel ridges

outer folded part of grey matter

inside is white matter that branches to all parts of the cerebellum

17
Q

list some functions of the hypothalamus

A

regulates body temperature

regulates autonomic nervous system: heart rate, blood pressure

regulates food and water intake

secretion of hormones

18
Q

what 3 components is the brain stem composed of

A

medulla oblongata

pons

midbrain

19
Q

what is the role of the medulla oblongata

A

important role in automatically adjusting body functions

regulates swallowing, sneezing, coughing, vomiting

contains 3 centres:

  1. cardiac: rate and force of heartbeat
  2. respiratory: rate and depth of breathing
  3. vasomotor: diameter of blood vessels

INFLUENCES BY HYPOTHALAMUS AND OTHER HIGHER CENTRES OF THE BRAIN

20
Q

explain the functions of the spinal cord

A

carry sensory impulses to the brain and motor impulses away from the brain

integrate certain reflexes.

21
Q

list some changes that the autonomic nervous system causes

A

heart rate

blood pressure

digestion

pupil diameter

22
Q

what is meant by a fight or flight response

A

In threatening situations the balance between sympathetic and parasympathetic stimulation is upset and the sympathetic becomes dominant

Situations that involve fear-anger, stress, danger or competition provoke what is called a fight-or-flight response or alarm reaction

These responses prepare the body for increased activity

activation of sympathetic nervous system include:
- increase heart rate and force of contraction
- dilation of blood vessels in neccessary organs: liver,
heart, skeletal muscles
- dilation of airways in the lungs and increased depth and
rate of breathing

23
Q

what are ‘receptors’

A

Structures within the cell membrane that are capable to detect a change in the body’s internal or external environments

24
Q

list some different types of receptors

A

osmoreceptors

chemoreceptors

touch receptors

pain receptors

thermoreceptors

25
Q

explain what an osmoreceptor is

A

detect osmotic pressure/water balance. Located in the hypothalamus

26
Q

explain what an chemoreceptor is

A

detect specific chemicals

Detect smell and taste in the nose and mouth

Detect oxygen, carbon dioxide and pH in blood vessels, and are involved in the regulation of heartbeat and breathing rate

27
Q

explain what an thermoreceptor is

A

detect heat and cold

In skin – detect external temperatures

In hypothalamus – detect internal body temperature

28
Q

what is a reflex

A

Rapid, automatic response to a change in the external or internal environment

mostly coordinated by spinal cord

The impulse may be passed to motor neurons at the same level in the cord, or may travel a few segments up or down the cord before travelling out through a motor neuron

In these cases the reflex is carried out by the spinal cord and is known as a spinal reflex

29
Q

what are the 4 properties of reflexes

A

A stimulus is required

Involuntary

Rapid response

Stereotyped

30
Q

what is a reflex arc

A

The pathway a nerve impulse follows in travelling from a receptor to an effector

or in the case of a spinal reflex, a spinal reflex arc

31
Q

what are the components (what happens) in a reflex arc

A

The receptor reacts to a change in the internal or external environment by initiating a nerve impulse in the sensory neuron.

A sensory neuron carries impulses from the receptor to the CNS

There is at least one synapse. The nerve impulse may be passed directly to a motor neuron or there may be one or more interneurons

A motor neuron carries the nerve impulse to an effector – away from CNS

An effector receives the nerve impulse and carries out the appropriate response. Effectors are muscle cells or excretory cells.

32
Q

what are learned reflexes

A

More complex motor patterns appear during a baby’s development – e.g. sucking, chewing, following movement with eyes

These innate reflexes are determined genetically

Some complex motor patterns are learned and are called acquired reflexes

They are learned through constant repetition

33
Q

what is the difference between the somatic and autonomic nervous system

A

SOMATIC:

  • carries message to skeletal muscles
  • neurotransmitter used is acetylcholine
  • one nerve fibre from CNS to effectors - no ganglion and synapse
  • voluntary

AUTONOMIC:

  • carries messages to involuntary muscles and glands
  • neurotransmitter used is acetylcholine or noradrenline
  • 2 nerve fibres from CNS to effector - with a synapse in a ganglion
  • involuntary

Human bio (16 decks)

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