OCR Biology Plant & Animal responses 5.1.5 revision summary - By A* student

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.
- Stimulussensory receptorsensory
neuronesynapserelay neuronespinal cordmotor
neuroneeffector
- 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