Nervous System Flashcards by Francisco Campino

Two parts of Nervous System

-CNS (brain, spinal chord)
-Peripheral NS (all other neurones that connect CNS to rest of the body)

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Two parts of PNS

-Somatic nervous system
-Autonomic nervous system

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Function of somatic NS

under conscious control, voluntary actions
single neurone links SNS to effector
Neurones are myelinated along axon
NT released by motor neurones= acetylcholine

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Function of Autonomic NS

under subconscious control, involuntary actions eg (heartbeat)
2 neurones link CNS and effectors- connected via ganglion
Myelinated until ganglion, unmyelinated after
pre ganglionic NT= ach

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ANS further divided into:

Parasympathetic NS (decreases activity)
postganglionic NT: ach

Sympathetic NS (increases activity)
postganglionic NT: noradrenaline

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Parasymoatehtic NS nerve

Vagus nerve

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Sympathetic NS nerve

sympathetic nerve

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5 regions of the brain

cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland

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Cerebrum role

-consists of 2 hemispheres
-controls conscious thoughts, language, emotional responses etc

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cerebellum

controls muscle coordination, balance & posture, reflexes

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Medulla oblongata

Controls autonomic activities in body eg. heart rate, breathing rate, blood pressure etc

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Hypothalamus

homeostasis

osmoregulation

Production of hormones which are then stored in the posterior pituitary gland

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Pituitary gland function

-Posterior: stores & secretes hormones produced by hypothalamus

-Anterior: produces & secretes hormones

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What is an axon

singular elongated nerve fibre
Transmits nerve impulses AWAY (a for axon) from cell body

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Importance of myelin sheath

Made of Schwann cells WRAPPED AROUND AXON
Insulate the axon
Makes it impermeable to Na and K ions, SO ions cannot pass in and out of neurone
There are small gaps- Nodes of Ranvier
These gaps are sites of depolarisation
Enable saltary conduction
Therefore faster conduction of the nerve impulse

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Action potential def

the change in electrical potential with the passage of an impulse along the membrane of a neurone

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what is resting potential

when a neurone is not transmitting an impulse or action potential

outline the procedure of an action potential

Resting Potential (-70mV)
Established by Na/K pump. 3 Na out, 2 K in
Depolarisation
Stimulus causes Na voltage gated channels to open
Na diffuse into cell
Inside more +, even more Na channels open (+ feedback
Action Potential (+30 mv)
Na channels close, K channels open
Membrane starts to return to resting potential
Repolarisation
Na/K pump restores ionic balance
Time for depolarisation- refractory period
Hyperpolarisation (dip)
Overshoot of K
Membrane potential is less than -70
Pump restores resting potential

What is the purpose of the refractory period

prevents action potential from going in reverse
-eg. cardiac muscle, refractory period allows time for chambers to refill

Why do action potentials travel faster in myelinated

-Depolarisation can only occur at nodes of Ranvier
-with myelinated, action potential jumps to the next adjacent node
-so speed of action potential transmission is sped up

Factors affecting speed of action potential transmission

-Temp (more kinetic energy)
-Axon diameter (less resistance)

what is a synapse

region between 2 neurones
impulses are transmitted across synapses using diffusion of NT

types of NT

-excitatory: depolarisation, triggers AP
-inhibitory: hyper polarisation, prevents AP

Feature of synaptic knob

many mitochondria & SER
voltage gated Ca2+ channels

outline the process of synaptic transmission

Action potential reaches pre-s knob Depolarisation causes Ca channels to open Ca ions flow in Synaptic vesicles triggered to fuse with pre-membrane NT released via exocytosis into cleft NT binds to specific, complementary receptors on post-s membrane Na+ channels on post-s membrane open If sufficient open, to overcome threshold value, action potential is generated

what happens to NT after synaptic transmission

NT broken down by enzymes in the cleft products reabsorbed by pre-s knob by endocytosis reformed using ATP & packaged into vesicles to be used next time

Why do synapses only allow transmission in one direction

Ca ions are only present at the presynaptic membrane

Excitatory postsynaptic potential

Increases likelihood of AP occurring NT causes membrane to become more positive closer to the threshold value

Inhibitory postynaptical potential

decreases likelihood of AP occurring NT causes membrane to become more negative & further away from threshold value

Summation & control

Sometimes NT quantity is low and not enough to excite postsynaptic membrane to a threshold value -Spatial summation: when several pre-synaptic neurones connect to 1 post-synaptic neurone -Temporal summation: several sub threshold build up in synapse until quantity is high enough to trigger action potential

what is a reflex

rapid, involuntary response to a stimuli to prevent harm to body

what is the plantar reflex

bottom of foot poked normal: flex down abnormal: flex up- indicated spinal cord damage

pupillary light reflex

both pupils should constrict to the same degree- if otherwise, possible damage to optic nerve

Advantages of reflexes

involuntary Rapid Do not have to be learnt

aquired brain injury

any brain injury after birth

how does a stroke occur

blood vessel supplying brain becomes blocked or blood vessel ruptures & bleeds into the brain

when is a patient considered dead

when there is no activity in the brain stem

how could drugs be used to treat alzeihmers

-Cholineesterase inhibitors -Prevent breakdown of Ach to choline -inc Ach conc -inc functioning

Causes and symptoms of Parkinson's

due to loss of brain cells that produce dopamine results in joint rigidity and slow movement drugs which could be used to treat Parkinson's: levodopa, dopamine agonists

addiction

uncontrolled, compulsive behaviour tolerance builds up- inc quantities required to produce the same effect

suggest why a person taking heroin may develop a psychological dependency

drug induces a *false* feeling of well-being so persons falls into the habit of taking drug to feel good