HB TOPIC 2- NERVOUS SYSTEM

1. Define Nervous system

   • define

   • 2 types

• communication network and control centre of the body

• Central Nervous system and Peripheral Nervous system

1. Difference between CNS and PNS

• CNS- brain and spinal chord

• PNS- Nerves connecting the central nervous system with limbs and organs

1. Define Neuron

   • define

• specialised cell that transmits signals by generating electric currents

1. Label Parts of Neuron

1. Nucleus

2. Dendrites

3. axons

4. cell body

5. myelin sheath

6. Schwanns cells

7. Nodes of Ranvier

1. Function of Dendrites

• extensions of cytoplasm that deliver messages/ never impulses from surrounding neurons to cell body

1. Function of axons

• long extensions of cytoplasm that carry messages away from body

1. Role of Myelin Sheath

   • define

   • role

• white lipid layer covering most axons

• Speeds up transmission by…

  1. acting as an insulator

  2. protects axons from damage

  3. speeds up nerve impulses

1. 3 types of neurons CLASSIFIED BY FUNCTION

   • list them

   • function

1. sensory/ receptor- carry messages from receptors to CNS

2. Motor/ effector- carry messges from CNS to muscles/glands

3. Interneurons- link sensory and motor in CNS

List type of nerve cells by structure

1. Multipolar

2. Bipolar

3. Unipolar

4. Pseudonipolar

1. Structure of Multipolar Neurons

   • structure

   • which are common

• one axons, multiple dentrites

• interneurons and motor

1. Structure of Bipolar Neurons

   • structure

   • examples

• one axon and one dendrite

• sensory neurons and interneurons

1. structure pf pseudonipolar neurons

   • structure

   • examples

one cell body to the side of the axon, one extention connects to dendrite and the other to axon terminals.

Sensory neurons

1. Define nerve fibres

• long extensions of cytoplasm from cell body (usually axon)

1. Define nerve

• bundles of nerve fibres held tg by connective tissue

1. Neurotransmission

   • define

• transfer of a message from the axon of one neuron to the dendrite of another

1. Define synapse

Gaps between adjacent neurons where signals are passed across

2. Define electrochemical change

change in electric voltage caused by changes in ion concentrations in and out of neuron

2. define potential difference

• potential for positive and negative ions to come together and release energy

2. How does extracellular fluid start before nerve impulses?

   • pos/neg

   • concentration of Na+ and Cl-

   • Permeability of each

• Starts positive

• 10x Na+ outside- slightly permeable due to limitied sodium leakage channels

• High concentration of Cl ions- highly permeable through protein channels

2. How does intracellular fluid start?

   • pos/neg

   • concentration of?

   • permeability of each

• Negative

• high concentration of K+, - highly permeable due to pottassium leakage channels

• high concentrations of organic ions- inpermeable

2. Define Membrane potential

• difference in charges between outside and inside of cell membrane

2. Resting membrane potential define

• unstimulated neuron with potential difference of -70mV (inside of cell is 70mV less than outside)

2. Steps of Neurotransmission

1. Neuron at rest

2. Stimulus

3. Threshold and depolarization

4. Repolarization

5. Hyperpolarization

6. Return to resting potential

2. Step 1- Neuron at rest

• resting potential at -70mv

• na+ ions are outside membrane and k+ ions are inside the membrane

2. Step 2- Stimulus

• causes gated sodium channels to open= some na+ ions into the cell

• results in cell becoming more positive inside

2. Step 3- Threshold and Depolarization

• if signal reaches threshold (-55mV), it triggers action potential.

• sodium fated ion channels open= more na+ inside and positive to 35.

• DEPOLARISATION- membrane charges reverse

2. Step 4- Repolarization

Peak voltage +35mV= gated sodium channels to close, and pottasium channels to open.

k+ moves outside and Na+ ions stay inside= repolarization

2. Step 5- Hyperpolarization

• more K+ ions outside than Na+ ions on the inside.

• cell membrane potential drops below resting potential

2. Step 6- Return to resting potential

• Sodium pump moves Na+ ions to outside and K+ to inside so cell returns to normal polarized state.

2. Define refractory period

• once sodium channels have opened, they are inactive and unresponsive to no new action potential can be generated during this time.

2. Define all or nothing law

If cell stimulus exceeds threshole of -55mV, nerve will give a complete response- otherwise there is no response

2. Myelinated axons

   • explain how it works

Nerve impulses travel faster along myelinated axons as the myelin sheath insulates axons from extra cellular fluid. Thus action potential must jump from one node of Ranvier to another.

3. Define Neurotransmitters

• chemical messengers that allow communication between neurons

3. Explain the steps of Neurotransmission

1. Action potential arrives at axon terminal of presynaptic cell

2. voltage gates calcium channels open

3. calcium ions enter the cell

4. calcium ions signal vesicles (containing neurotranmitters) to move to presynaptic membrane

5. vesicles release neurotransmitters via exocytosis to synaptic cleft

6. neurotransmitters diffuse across synaptic cleft and bind to receptors of POST SYNAPTIC CELL

7. If enough bind, stimulates new action potential by opening sodium ion channels

8. neurotransmitters leave receptors and reuptaken into either vesicles or broken down.

3. List the effects of chemicals on neurotransmission- and their effects

1. Stimulants (eg, caffiene)- indicate transmission at synapse

2. Depressants (weed)- slow/ prevent transmission

3. Venom- blocks neurotransmission at neuromuscular junction= paralysis

4. organophosphates- build up of acH NT= muscles of body contract and no breathing.

4. Define Ganglion

• group of cell bodies outside brain and spinal chord

4. Cranial nerves

   • how many pairs

   • what do sensory and motor neurons do?

• 12

• sensory- carry impulses from receptor to brain

• motor- carry impulses from brain to muscle

4. Spinal nerves

   • how many pairs

   • where are sensory and motor neurons located?

   • where are the cell bodies located

• 31

• Motor Neurons in VENTRAL ROOTS- cell bodys in grey matter

• Sensory Neurons in DORSAL ROOTS- cell bodies in dorsal ganglion

4. What are the 2 types of PNS?

1. Sensory Afferent

2. Motor Efferent

4. PNS- Sensory Afferent- what are the 2 types of nerve fibres and their functions?

1. Somatic sensory- carry signals from bones, skin joints and muscles

2. Visceral sensory- carry signals from

4. PNS- Motor Afferent- what are the 2 types of nerve fibres and their functions?

1. Somatic motor- controls volentary movement of muscles

2. Autonomic motor- controls automatic functions and has 2 divisions

4. What are the 2 divisions of the autonomic motor?

   • and regulated by?

1. Sympathetic- arouses body for action eg. fight or flight

2. Parasympathetic- calming effect

Regulated by medulla oblongata, cerebral cortex, and hypothalamus

4. fight or flight response

   • controlled by..

   • explain some eg, of what happens

• sympathetic

• oxygenated blood to brain and msucles

• increased HR

• airways open up

4. Differences between Hormone/Nervous system

1. Nervous = rapid (miliseconds), Hormone- slow via blood stream

2. Nervous- stops when stimulus ends, Hormone- slower response

3. Nervous= electrochemical change, Hormone= chemical hormones

4. Nervous- specific parts of body, Hormone= multiple parts of body or whole body

4. Similarities between Nerv/Horm System

1. some are both NT and hormones eg. dopamine

2. some have the same effect on target cells eg. noradrenaline and glucagon

3. some hormones are excreted by neurons

5. CNS is protected by…

1. Bone

2. Meninges

3. Cerebrospinal fluid

5. Protection of CNS- Bone

   • Define

Outermost protective layer of brain that consistents of bone to make up cranium

5. Protection of CNS- Meninges

   • list the 3 types and function

1. Dura Mater (outer)- tough and fibrous tissue to provide protection against forces

2. Arachnoid mater- loose mesh of fibre to hold cerebrospinal fluid in place

3. Pia mater (inner)- delicate and sticks closely to surface of brain containing blood vessels

5. Protection of CNS- Cerebrospinal fluid

   • define

   • where is it found?

   • function

• clear watery fluid

• found between meningeal layers and circulates the brain cavities and spinal chords

• Acts as shock absorber or supports brain inside cranium

5. Name the parts of the cranium and their roles

1. Frontal lobe- cognition, reasoning etc

2. Parietal- information and senses

3. Temperal lobe- hearing memory and comprehension

4. Occipital lobe- vision

5. Insula lobe- emotions and addiction

5. Structure of Cranium

• longitudinal fissure- deep groove to seperate hemispheres

• gyri- thick folds

• sulci- shallow grooves

• corpus collsum- bundle of nerves that conect the hemispheres

6. Types of Receptors- list them all, role and where theyre found

1. pain- trauma to tissue- found everywhere except brain

2. Touch- close to surface of skin and found everywhere

3. Thermoreceptors- central and peripheral- detect changes in temp near skin or in blood

4. Osmoreceptors- detect changes in osmotic pressure in hypothalamus

5. Chemoreceptors- detect chemicals in mouth nose, and blood.

6. Define reflexes

• rapid automatic response to a change in external or internal environment

6. Features of reflexes

1. must be stimulated

2. rapid

3. automatic/ involentary

4. stereotypes- same each time

6. Steps of a reflex arc

1. Receptor- sensory neuron detects change and starts nerve impulse

2. Sensory neuron carries message from PNS to CNS

3. Synapse- nerve impulse to interneuron or sraight to motor

4. Motor- carries impulse to effector

5. Effector- recieves nerve impulse and responds.