the nervous system Flashcards

1
Q

what are the components of the reflex arc

A

1) Stimulus
2) Sensor/integrator neuron
3) relay neurones
4) muscle or other effector neurone
5 ) response

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1
Q

what features led to the evolution of centralization and cephalization

A

centralization= the local concentration of neurones
cephalisation= development of brain like tissues from increasing concentrations of nervous tissues

1) Nerve nets are the most simple nervous system= just a network of cells

2) simple ganglia and nerve rings evolved for more complex behaviour such as in radial symmetric animals like starfish

3) a true CNS evolved with bilateral symmetry= centralisation began with longitudinal nerve cords coordinating nervous activity
4) True brains evolved at the anterior end of complex animals= the anterior end of the CNS was larger and contained sizable clusters of neurones aka the brain

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2
Q

why are complex ganglionic nervous systems characteristic of advances non-verterbrates

A
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3
Q

how does the expensive tissue hypothesis explain relative brain size

A

the metabolic cost of neural tissue is comparatively high due to energy needed to maintain the membrane potential across axonal membranes = very energy intensive
therefore the larger the brain the greater energy expenditure

this means animals increased brains size cant be achieved without a increase in quality of diet seen in carnivores and herbivores- carnivores have bigger brains as they have better diets

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4
Q

compare the regulatory systems known as nervous control and hormonal control

A

Nervous= CNS & PNS, electrochemical signalling, nerve impulses and neurotransmitters, Rapid short term responses, localised effect, target effectors

hormonal= secretory cells, chemical signalling, hormones in blood stream, wide spread effect, many cells

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5
Q

what is a membrane potential

A

a separated unbalanced charge across the membrane
resting potential in all cells is at -70mv

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6
Q

what causes changes in membrane potenital

A

triggering events which alter the membrane ion permeability of gated ion channels which are sensitive to changes in voltage and when there is one they open allowing passive movement of ions down conc gradient into the cell

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7
Q

what are the different types of potential

A

1) Graded = generated from sensory input causing a change in the conductance of the membrane cell and are localised to active areas, they decay very rapidly

2) Action= a result of large and rapid changes in membrane potential when a graded potential reaches threshold (-30mv) causing it to be propagated without decay due to positive feedback mechanisms causing rapid influx of ions

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8
Q

outline how an action potential is generated

A

1) Resting potential= all channels are closed
2) threshold is met and Na+ channels open resulting in depolarisation and positive feedback
3) rapid influx of Na+ into cell and at peak inactivation gate closes causing K+ channels to open for repolarisation
4) Na+ channels conformation resets
5) hyperpolarisation occurs
6) K+ channels shut returning to resting potential where Na+/K+ ATPase channels restore resting potential

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9
Q

what part of the axon do graded and action potentials occur

A

Dendrites = only graded potentials can occur but if they reach threshold they trigger action potentials in the axon hillock

axon= automatic conduction of action potential towards axon terminals

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10
Q

What are the different types of synapse

A

1) Electrical= gap junctions in which transmission jumps to next neurone causing rapid transmission

2) Chemical synapses= use of neurotransmitters allowing different messages to be sent in one direction, occurs more slowly than electrical

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11
Q

what is a refactory period

A

A refractory period is a period of time during which an excitable membrane is incapable of repeating an action potential. It occurs after an action potential is generated and until the resting potential is re-established
ensures one way flow and limits number of action potentials

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12
Q

outline of a message is sent across chemical synpases

A

1) Action potential reaches axon terminal of presynaptic neurone

2) Calcium enters synaptic knob causing release of neurotransmitter into synaptic cleft by exocytosis

3) NT binds to receptors on chemically gated channels on subsynaptic membrane of postsynaptic neurone

4) Binding of NT to receptor opens specific channel causing another action potential to be generated

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13
Q

what is the difference between afferent neurons and efferent neurons and interneurons

A

A = transmits signals from sensory receptors to the CNS

E= transmit information from CNS to effectors

I= transmits information between afferent and efferent neurones

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14
Q

what is the autonomic nervous system

A

responsible for regulating involuntary physiological processes

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15
Q

what is the sympathetic and parasympathetic nervous system

A

work together to produce opposing effects to each other producing a balance between the two

16
Q

what is dual innervation

A

have nerves from both systems going to same systems allowing precise control

17
Q

what is the difference between preganglionic fibres and postgaglionic fibres

A

1) pre= interneurons in CNS
- where there is a junction between CNS and peripheral NS
- neurotransmitter is always acetylcholine

2) post ganglionic fibre
- different NT depending on branch NS
- sympathetic = NE
- parasympathetic = acetylcholine

by releasing different transmitters allowing dual innervation allowing different systems to act on same tissues

18
Q

compare the ANS to the SNs

A

Site of origin
ANS= Brain/lateral horn of spinal cord
SNS= ventral horn of spinal cord

Number of neurones
ANS= two neuron chain (pre and post ganglionic
SNS= single neurone (motor)

organs innervated
ANS= cardiac muscle, smooth muscle exocrine
SNS= skeletal muscle

effect on effector organs
ANS= stimulator/inhibition
SNS= subject to both reflex and non reflex control

higher centres involved
ANS= spinal cord, medulla, hypothalamus, prefrontal association cortex
SNS= spinal cord, motor cortex, basal nuceli, cerebellum and brain stem