A revision summary of OCR A level Biology Plant & Animal responses 5.1.5
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
The Nervous system (NS) – coordinate between sensors & effectors so an organism can respond to changes in its (internal/ external)
environment
- Detection of changed in internal/external environment Peripheral Nervous system (PNS)
- Cell signalling between all body parts Communication between sensory neurones, CNS & motor
- Coordination of range of effectors neurones
Central NS Sensory Motor
(CNS)
Brain
Spinal Somatic NS Autonomic NS
- Grey matter (non-
myelinated nerve 1. Sensory Cord
Neurones (dorsal root) Movement Conscious, voluntary Unconscious, involuntary
cells) - Cell body in dorsal root ganglion Effecters Skeletal muscle Smooth & cardiac muscle,
- White matter (longer - Receptor CNS glands
myelinated axons & 2. Relay Neurone (CNS) CNS: motor 1:1 1: multiple (ganglion)
dendrons) - In spinal cord grey matter neurone
- Sensory Motor Neurotransmitter Acetylcholine (ACh) ACh/ Noradrenaline
3. Motor neurones (ventral root) Summation excitatory Excitatory & inhibitory
- Cell body in CNS
Neurones myelinated Non-myelinated
- CNS effector
Control
cell centre Cerebrum Homeostatic centres in brain
Ganglion – swollen region of nerve where
bodies of neurones are grouped together Sympathetic Parasympatheti
c
NT at effector Noradrenaline ACh
Preganglionic fibre Short Long
Ganglion Outside CNS Effector tissue
Postganglionic fibre Long Short
Effects Prepares Conserves energy
activity Rest & digest
Fight/ flight
Human brain
Cerebrum 2 cerebral hemispheres connected via corpus collosum.
Controls higher brain functions – conscious thought, learning, memory,
emotion
4 lobes; Frontal, parietal, occipital, & temporal.
- Each lobe specific to role & contralateral
- Motor cortex send action potential to effectors.
- Sensory cortex receives info form sensory receptors
Cerebellum Co-ordination of unconscious ‘learned’ voluntary movements
Fine motor control – posture, balance
Medulla Autonomic control - involuntary
oblongata Non skeletal muscles - Heart rate, breathing, reflex
Hypothalam Homeostasis mechanisms (-ve feedback) – body temp, water balance
us
Pituitary Hormonal control
Gland Anterior – sexual control, secretes FSH
Posterior – releases ADH
, Reflex – responses to changes in the environment that do not
involve any processing by the brain to coordinate movement.
- Stimulussensory receptorsensory
neuronesynapserelay neuronespinal cordmotor
neuroneeffector
- Uses spinal cord to make reflex arc shorter & quicker
- For survival: protection, no learning, rapid, involuntary
Cranial reflex - passes Spinal reflex – neural circuit
through the brain but is only to spinal cord
requires no thought
Corneal reflex – Knee-jerk Reflex –
involuntary response when involuntary forward movement
cornea is stimulated to of the lower leg produced
protect eye from damage/ maintain balance.
dust.
1. Sensory neurone takes 1. Tapping tendon pulls on
impulse from cornea quadricep muscle
Pons 2. Sensory receptors (Spindle
2. In Pons, synaptic fibres) stretch & send
transmission: action potential to sensory
Sensory Relay neurone
Motor 3. Sensory neurone
3. Motor neurones Motor neurone (in CNS)
transmit action 4. Motor neurone causes
potential out Pons to contraction of quadricep
facial muscles = blink.
Synapse = relay neurone, No synapse = no relay
can be inhibited, slower. neurone, cannot be inhibited,
faster/
Overriding corneal reflex
- Action potential passed to sensory region in cerebral
cortex, informing brain of reflex allowing input of conscious
control.
- Inhibitory signals sent to motor centres in Pons which
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