Coordination (Chapter 10)
- Created by: Tassillow
- Created on: 30-05-16 18:56
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- Coordination
- Neurones
- Structure of Neurones
- cell body
- nucleus
- large amount of RER
- proteins
- neurotransmitters
- myelin sheath
- covering of axon made of schwann cells
- rich in myelin lipid
- faster impulses
- Schwann cells
- surround axon in layers
- electrical insulation
- phagocytosis
- nerve regeneration
- nodes of Ranvier
- every 1-3mm
- gaps between schwann cells
- 2-3 micrometers long
- Axon
- single long fibre
- impulse away from cell body
- Dendrons
- small extentions of cell body
- branch into dendrites
- impulse towards cell body
- Neurone classifications
- Sensory
- receptor > relay
- one dendron
- Motor
- relay > effector
- long axon
- many short dendrites
- Relay
- between neaurones
- numerous short purposes
- Sensory
- cell body
- Structure of Neurones
- Coordination
- Plant Growth Factors
- plants have no nervous system
- Respond to
- Gravity
- to be firmly anchored into soil
- Roots
- Positive geotropism
- Light
- stems
- positive phototropism
- for photosynthesis
- Water
- roots
- positive hydrotropism
- for
- photosynthesis
- Metabolic processes
- support
- Gravity
- Name better than hormones
- affect growth
- made by cells throughout organism not organs
- some affect releasing tissues
- produced in small quantites
- e.g. indoleacetic acid (IAA)
- Chemical Mediators
- cellular level
- Mammalian
- chemicals effecting cells in immediate vicinity
- typically released by cells that are
- injured
- infected
- cause
- small arteries and arterioles dilate
- inflammatory response
- Swelling
- Temperature rise
- e.g.
- histamine
- stored in WBCs
- released
- injury
- allergen
- Causes
- increased permeability of capillaries
- dilation of small arteries and arterioles
- syptoms
- swelling
- redness
- itching
- prostaglandins
- in cell membranes
- causes
- dilation of small arteries and arterioles
- increased permeability of capillaries
- affect blood pressure
- affect neurotransmitters
- affect pain sensation
- released following injury
- histamine
- Control of tropisms by IAA
- Light
- stems
- elongation
- Gravity
- roots
- decreases growth
- Steps
- 4.greater [IAA] on shaded side
- 3.light causes it to move to shaded side
- 5.IAA causes shadey side to elongate
- 2.transported to all sides initially
- 6.shoot bends towards light
- 1.tip produces IAA which travels down shoot
- Light
- Principles of coordination
- Nervous system
- nerve cells
- Electrical impulses
- Secrete neurotransmitters directly onto target cells
- Rapid
- short lived
- localised
- e.g.
- Reflex actions
- drawing hand away from harmful stimulus
- Hormonal system
- chemicals
- transported in blood plasma
- slow
- long-lasting
- Widespread
- e.g.
- control of blood glucose
- Nervous system
- Plant Growth Factors
- The Nerve Impulse
- Action Potential
- Process
- 4.+40mV
- Na+ channels close
- K+ channels open
- 3.More Na+ channels open
- due to changed voltage
- greater influx
- 5.Repolarisation
- electrical gradient reversed
- more K+ channels open so more diffuse out
- 2.Stimulus triggers depolarisation
- some Na+ voltage gated channels open
- Na+ in due to electrochemical gradient
- 6. hyper polarisation
- temporary overshoot
- K+ channels close
- Sodium-Potassium pump reastablish -65mV
- 1.Resting potential
- K+ channels open
- Na+ channels closed
- 4.+40mV
- temporary reversal
- depolarisation
- -65mV > +40mV
- due to voltage gated channels
- Process
- Resting Potential
- Movement of ions controlled
- Ptorein channels
- intrinsic proteins
- some gated
- allow ions through some times
- types
- Ligand
- voltage
- some open all the time
- diffusion
- Phospholipid bilayer
- of axon
- no ion diffusion accross it
- sodium-potassium pump
- intrinsic proteins
- active transport
- potasssium ions in
- Sodium ions out
- Ptorein channels
- Established due to
- Naturally diffuse down gradient
- chemical gradient
- although both positive
- More Na+ in tissue fluid
- more K+ in cytoplasm
- gates
- K+ open
- Na+ closed
- 3 Na+ out for 2 K+ in
- potential difference increased
- K+ diffuse out faster than Na+ diffuse in
- 100x more permeable to K+
- K+ in by sodium-potassium pump
- Electrical gradient
- tissue fluid more positive
- K+ held inside of axon due to repelling and attractive forces
- Na+ out by sodium-potassium pump
- Equillibrium
- no net ion movement
- Polarised
- inside more negative than outside
- ~65mV
- Movement of ions controlled
- Action Potential
- Passage of an Action Potential
- Along an unmyelinated axon
- Mexican wave analogy
- wave moves around stadium
- Individuals stay still
- Process
- 3.Localised circuit means depolarisation occurs a little further along
- 2.Stimulus causes depolarisation
- 4.depolarisation continues along axon, hyper polarisation occurs
- 1.Resting Potential
- 5.Resting potential re established
- Mexican wave analogy
- Along a Myelinated axon
- Action potentials cannot form over myelin
- Saltatory conduction
- Faster than unmyelinated
- Localised circuit longer
- action potential jumps between nodes of ranvier
- Along an unmyelinated axon
- Speed of the Nerve Impulse
- Refractory Period
- impossible for new action potential
- Na+ gates closed
- Na+ cannot enter axon
- Purpose
- One direction only
- active region > resting region
- no propogation in refractory region
- would otherwise spread out in both directions
- discrete impulses
- seperated
- cannot be formed immediately behind eachother
- limits number of action potentials
- seperated
- limits number in given time
- One direction only
- Factors effecting Speed of impulse
- Myelin sheath
- electrical insulator
- saltatory conduction
- action potential only at nodes of ranvier
- 30ms-1 unmyelinated > 90ms-1 myelinated
- axon diameter
- larger diameter = faster
- less leakage of ions
- Temperature
- higher = faster
- increases rate of diffusion
- energy for active transport comes from repiration
- enzyme controlled
- faster up till certain point
- enymes denature after certain point
- Important factor for response time of ectotherms
- Myelin sheath
- All-or-nothing principle
- Above threshold = impulse
- Below stimulus = no impulse
- how size of stimulus percieved
- more frequent = larger
- different neurones with different thresholds
- Refractory Period
- Structure and Function of Synapses
- Functions
- Junctions
- single > many
- single stimulus
- simultaneousresponses
- many > single
- stimuli from many receptors
- one reponse
- single > many
- neurotransmitter made only in pre
- neurotransmitter released due to action potential
- neurotransmitter diffused across cleft
- neurotransmitter binds to receptor and starts new action potential
- Junctions
- Features
- Summation
- Two types
- Low frequency action potentials do not produce new action potential in post synaptic neurone
- Untitled
- Uni directionality
- pre > post
- act like valves
- Inhibition
- post synaptic membrane
- ligand gated Cl- channels open
- more negative than resting potential
- hyper polarisation
- as Cl- in
- action potential less likely
- Summation
- Structure
- Synaptic cleft
- gap seperating neurones
- 20-30nm
- neurotransmitter
- diffuse across
- presynaptic neurone
- axon ends in synaptic knob
- many mitochondria and RER
- synaptic vesicles
- Store neurotransmitter
- fuse with membranse to release
- postsynaptic neurone
- receptors
- Synaptic cleft
- Functions
- Transmission Across a Synapse
- Neurones
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