3: Nervous system

Question 1

Define homeostasis

Answer 1

the process by which the body maintains a relatively stable internal environment.

Question 2

What are the 3 systems that maintain homeostasis

Answer 2

1- sensory function (detects and sends)
2- Integrative function (analyses, interprets and generates a response)
3- motor function (issues output)

Question 3

Define general sensory receptors

Answer 3

located in the skin, skeletal muscles, tendons, joints and visceral organs. 
Include;
thermoreceptors 
nociceptors 
mechanoreceptors

Question 4

What does the general sensory receptor thermoreceptors detect?

Answer 4

detect changes in the temperature

Question 5

What does the general sensory receptor nociceptors detect?

Answer 5

detect painful stimuli

Question 6

what are the three types of mechanoreceptors and what do they detect

Answer 6

tactile- touch, pressure and vibration
Baroreceptors- blood pressure
proprioceptors- changes in body position (proprioception)

Question 7

Where are special sensory receptors located?

Answer 7

eyes, ears, mouth and nose

Question 8

What are some examples of special sensory receptors

Answer 8

photoreceptors- detect light (vision)
Chemoreceptors- detect chemical solutions (taste and smell)
Mechanoreceptors called hair cells (detect hearing and balance)

Question 9

What are the two divisions of the nervous system?

Answer 9

CNS and PNS

Question 10

CNS structures and functions

Answer 10

structure= brain and spinal cord 
Function= control centre that performs integration 

• controls emotions, behaviours and personality
• performs intellectual (cognitive) functions
• stores memories

Question 11

PNS structures and functions

Answer 11

structure= contains sensor receptors, cranial, spinal and peripheral nerves.

Question 12

Cranial nerves structure and function

Answer 12

branch primarily innervate structures of the head and neck.

Question 13

Spinal nerves structure and function

Answer 13

Spinal nerves branch to form the peripheral nerves that innervate all parts of the body below the head.

Question 14

What are the two divisions of the peripheral nervous system?

Answer 14

sensory (afferent)
- conveys sensory input from receptors to the CNS

motor (efferent)
- converts the motor output from CNS to muscles or glands

Question 15

What are the two divisions of the motor division?

Answer 15

autonomic and somatic

Question 16

Describe the somatic nervous system and what it controls.

Answer 16

conveys somatic motor output from CNS to skeletal muscles

Voluntary= skeletal muscle movement
involuntary= skeletal muscle movements (smoatic reflexes)

Question 17

Describe the somatic nervous system and what it controls.

Answer 17

conveys autonomic motor output from CNS to glands, cardiac and smooth muscles

controls involuntary activities

e. g.
- heart rate
- respiration (respiratory air flow)
- blood vessel and pupil diameter
- digestion of food
- urination and defecation
- perspiration and salivation

Question 18

What are the two functions of the autonomic nervous system

Answer 18

sympathetic

parasympathetic

Question 19

Describe the sympathetic division

Answer 19

“fight or flight”- activities
- activated the body functions that support physical activity and inhibits those that don’t.

• increases heart rate, respiratory air flow, blood flow to skeletal muscles and sweat gland activity.
• dilates pupils
• inhibits digestive function
• inhibits urination and defecation

Question 20

Describe the parasympathetic division

Answer 20

“rest and digest”- activities

• conserves energy and promotes the body’s housekeeping functions
  e. g.
• stimulates digestive function, urination and defecation
• constricts pupils
• decreases heart rate
• decreases respiratory flow

Question 21

What are the two key components of the nervous system

Answer 21

• neuroglia

- neurons (nerve cells)

Question 22

Define neuroglis

Answer 22

“nerve glue”
support neuron development and function, nourish, protect, insulate and structurally support neurons

Most brain tumours are made of neuroglia.

6 main types

Question 23

What are the three basic functions of the nervous system?

Answer 23

1- detect chnages (stimuli) occuring inside and outside the body

2- respond to these changes by altering the activities of organ systems

3- coordinate the activities of all organ system

Question 24

What are the four main types of effectors

Answer 24

• skeletal muscles
• cardiac muscles
• smooth muscles
• glands

Question 25

Define neurons

Answer 25

the basic structure of the nervous system. Function: communication. - when stimulated they generate electrical signals called graded potentials and action potentials to conduct sensory and motor information from one part of the body to another. high metabolic rate - Needing a high supply of oxygen and glucose for survival. unable to divide and replace themselves if destroyed.

Question 26

What are the 4 main components of a neuron

Answer 26

1. Dendrites 2. cell body 3. axons (fiber) 4. axon terminals

Question 27

Describe dendrites

Answer 27

Structure= finger-like trees at the top of a nerve. Function= main receptive (or input) region - act as sensory receptors- detect stimuli Large surface area= allows them to detect stimulus and receive info effectively. convert info they receive to graded potentials which they send to cell body

Question 28

Describe the cell body

Answer 28

contains nucleus and organelles - crecieves info, intergrates and sends incoming information to the axon

Question 29

Describe the axon (aka fibre)

Answer 29

The conducting region. "conducting region" that generates (initial segment) and conducts action potentials to convey information from the initial segment to the axon terminal. - can be mylinated

Question 30

Axon hillock

Answer 30

conducting region between cell body and axon

Question 31

Describe myelin

Answer 31

``` structure= white and fatty function= speeds up transmission ``` produced by schwann cells and oligodendrocytes

Question 32

What diseases are associated with mylein damage

Answer 32

Loss of myelin slows myelin conduction and can determinate so much that conduction stops. Aka multiple sclerosis

Question 33

Define nodes of ravier (internodes)

Answer 33

gaps in the myelin

Question 34

Describe the axon terminal

Answer 34

synapses with another cell =secretory region - releases neurotransmitters (chemicals that carry info to another cell) - contain synaptic vesicles which store and release neurotransmitters (chemical that carry info)

Question 35

Where are nuclei (nucleus) and ganglia (ganglion) located and what are they?

Answer 35

nuclei (nucleus)= CNS ganglia= PNS - they are clusters of neuron cell bodies

Question 36

What is the function of nuclei (nucleus)

Answer 36

Function= integration - Analyse and interpret sensory input - Analyse and decide on a motor response. Some nuclei located in the brain - Store memory - Determine personality - Regulate emotion - Perform intellectual function - Produce hormones

Question 37

neuron axions are bundled to form what in where?

Answer 37

Tract in the CNS - conduct sensory and motor info through spinal cord and different areas of the brain. Nerves in the PNS -conduct sensory input to CNF and motor output away from CNS

Question 38

What are the three strutural clasifications of neurons and where are they found

Answer 38

Bipolar (cell body in the middle, unmylenated) - rare (in special sense organs e.g. ear, eye) unipolar (detached cell body) - PNS multipolar (regular looking) - CNS and PNS

Question 39

Structure and function of sensory neurons

Answer 39

``` S= uniploar F= sensory input from receptors to CNS ```

Question 40

Structure and function of interneurons

Answer 40

``` S= multipolar F= conduct information within CNS ```

Question 41

Structure and function of motor neurons

Answer 41

S- multipolar F= conduct motor output away from the CNS to a muscle or gland lower motor neuron= somatic motor output pre and post ganglionic= autonomic output

Question 42

The basic principle of RMP

Answer 42

opposite changes attract so energy is required to keep them apart. aka. potential energy stored/potential energy= measured in V or mV

Question 43

Define membrane potential

Answer 43

the potential energy that is separating the internal negative and the external positive changes

Question 44

When does a change in membrane potential occur

Answer 44

when an ion k+ leaves or Na+ goes into the cell changing the charge strength. this creates an electrical signal summary= ions flow across the plasma membrane of a neuron- membrane potential (voltage) changes- electrical signal generated

Question 45

What must a neuron do they generate an electrical signal

Answer 45

their plasma membrane must; - exhibit a resting membrane potential (RMP) - contain protein channels that allow specific ions to diffuse down their concentration gradient.

Question 46

What are the two main types of channels that let K+ and Na+ ions though to change membrane potential?

Answer 46

leakage channels= always open, the small number allowed to cross Gated channels= stimulated to open and close, large numbers allowed to cross summary= when a stimulus opens gated ion channels, multiple/large number of ions move across

Question 47

What are the three types of gated channels?

Answer 47

chemically gated mechanically gated voltage-gated

Question 48

Explain simulation and location of chemically gated channels

Answer 48

open in response to chemical signals e.g. neurotransmitter binds to a channel causing it to open. This means ions are free to cross location= along plasma membrane of dendrites and cell bodies

Question 49

Explain simulation and location of mechanically gated channels

Answer 49

open in response to mechanical stimulation e.g. touch, vibration and pressure location= along the plasma membrane of dendrites

Question 50

Explain simulation and location of voltage gated channels

Answer 50

Open and close response to voltage changes or changes in membrane potential. Location= along the plasma membrane od the axon and axon terminals.

Question 51

What gated channels are on the membranes of; dendrites cell bodies axons and axon terminals

Answer 51

Dendrites: mechanically and chemically gated channels Cell body: chemically gated Axon and axon terminals: voltage gated channels

Question 52

Define resting membrane potential (RMP)

Answer 52

= the voltage across the plasma membrane of a resting (unstimulated) cell it exists because of an uneven distribution of positive ions across the plasma membrane creates a charge difference across the membrane. ECF= overall positive ICF= overall negative

Question 53

what is the aprox RMP

Answer 53

-70mV

Question 54

Compare the ECF to ICF in terms of charge

Answer 54

ECF= high concentration of Na+ ions - more +ve ions - overall positive charge ICF= hugh concr=entration of K+ ions - less +ve ions - overall negative charge

Question 55

Depolarisation=

Answer 55

the membrane becomes less negative - means it moves from -70 towards 0. D= depolarise= decrease negativity sodium gated channels open letting Na= (more positive) into the less negative ICF----- this decreases the RMP to -60 e.g.

Question 56

Hyperpolarisation=

Answer 56

membrane becomes more negative when a stimulus opens K+ gated channels allowing a great number of K+ ions into the ECF, the ICF becomes more negative (loses positive K+ ions) RMP= more negative e.g. - 70mV to -80mV

Question 57

What happens to the RMP when hyperpolarisation and depolarisation occurs

Answer 57

``` hyper= more negative depola= less negative ```

Question 58

Explain graded potentials

Answer 58

- Small changes in membrane potential (de or hyperpolarisation) - Occur in dendrites or cell body when stimulus opens the chemically mechanically gated channels. - Short stimulus - strong stimulus= bigger change in membrane potential= further signal will travel

Question 59

Explain how a graded potential leads to an action potential

Answer 59

- once stimulated by chemical or chemical stimulant on cell body or dendrite occurs, a graded potential is created. The short burst is send to the initial segment. the stronger the stimulus= treating RMP change= signal will travel further - AP depolarises initial segment to -55mV = threshold - this stimulates voltage-gated Na+ channels to open - this generates AP Actions potential is generated if a stimulus is so loge the graded potential has enough strength to travel to the imitial segment wich depolarises the initial segment to -55mV= threshold which then stimulates voltage gated Na+ channels to open this then generates action potential.

Question 60

What are some properties of action potentials?

Answer 60

- long distance - originate at initial segment - involve voltage-gated channels - self propelling aka. fist AP triggers 2nd AP triggers 3rd AP

Question 61

Action potential are generated by what three consecutive changes in the membrane potential?

Answer 61

depolarisation depolarisation hyperpolarisation

Question 62

Describe depolarisation

Answer 62

once at -55mV, voltage gated chnannels open to let even more Na+ past to get it +30mV - occurs at -55mV (membrane has got less natuage when Na+ channels have opened up and Na+ comes in) - axon interior becomes less negative - membrane potential shifts from -55mV to +30mV

Question 63

Desctibe repolarisation

Answer 63

- occurs when membrane hits +30mV - voltage gated Na+ channels close and voltage gated K+ channels open to ket K+ out of the ICF - loss of K+ ions makes the RMP move closer to -70mV

Question 64

Describe hyperpolarisation

Answer 64

as the membrane aproaches -70mV it closes vo;tage gated channels however they are slow to close so K+ continue to flow into ECF - axon interior becomes more negative e.g. -70mV to -90mV - when K+ channels close, the movement of Na+ and K+ through leakage channels and ATPase pump resotres RMP back to -70mV

Question 65

Explain continuous conduction

Answer 65

- occurs in unmyelinated axons - AP generated at voltage-gated channels along the axon - slow conduction (< 2m/s)

Question 66

Explain saltatory conduction

Answer 66

- occurs in myelinated axons - action potentials generated at nodes of ravier - very fast >100m/s - signals skip and leap down axons via nodes od ravier

Question 67

How does localised anesthetic impact action potentials

Answer 67

- blocks sodium gated channels so no pain or sensation can be conducted to the brain - block pain transmission by blocking Na+ gated channels. Therefor no Na+ entering axon so no depolarisation occurs.

Question 68

Define a chemical synapse

Answer 68

A junction that mediates the transfer of information from one neuron to another or neuron to a muscle or gland. presynaptic neuron- post synaptic neuron through synaptic cleft via neuro transmitters

Question 69

Steps of information transfer

Answer 69

1- action potential arrives at axon terminal and depolarises 2- depolarisation stimulates voltage gated Ca2+ channels (on the membrane) to open and Ca2+ to enter the terminal 3- Ca2+ entrance triggers synaptic vesicles to release neurotransmitters into synaptic cleft 4- neurotransmitters diffuse across the synaptic cleft and bind to chemically gated channels on the post synaptic membrane of cell body or dendrite. 5- binding of neurotransmitter opens chemically gated channels- influx of Na+ into ICF=depolarisation= graded potential created (excitatory postsynaptic potential- EPSP)\- EPSP travels and depolarises at initial segment of post synaptic neuron to threshold 9-55mV= action potential generated - info successfully transmitted

Question 70

Describe the 3 terminations of synaptic transmission

Answer 70

1- neurotransmitters diffuse away from synaptic cleft 2- are degraded by enzymes in synaptic cleft 3- NT's re-enters axon terminal and is destroyed by enzyme or reused, aka re uptake