OCR Biology A level 5.1.5 Plant and Animal responses summary notes

 Increase in H+
 Detected by carotid receptors
 Increase in frequency of impulses
 Along accelerator nerve
o To diaphragm and intercoastal muscles
 Faster breathing
 Deeper breating
o To SAN
 Heart beats faster
 Increased stroke volume
 Faster removal of carbon dioxide
 Blood CO2 levels fall to norm
 Negative feedback




5.1.5 Plant and Animal responses

,Grey matter: consists
White matter: consists of mainly
of mainly nerve cell
myelinated axons and dendrons
bodies and of mainly (myelin makes the long fibres appear
non-myelinated nerve white)

Dorsal root: spinal nerve which carries
impulses from receptors to spinal cord




Ventral root: spinal nerve which
carries impulses from the spinal cord
to the effectors



Central:
- Consists of brain and spinal cord
- Contains intermediate neurones/relay neurones
- Has coordinating role/many synapses

Peripheral:
- Nerves run from sense organs (to CNS)/ muscles or glands (from CNS)
- Contains sensory and motor neurones
- Role in sensing stimuli/controlling effectors (conducting impulses to & from CNS/brain)
- Includes somatic and autonomic nervous system (made up of sympathetic and parasympathetic)
o SOMATIC: controls voluntary/conscious actions
 Somatic motor neurones carry impulses from the CNS to skeletal muscles which are
under voluntary control
 Have cell bodies in the CNS
 Mostly myelinated
o AUTONOMIC: controls unconscious/involuntary actions

,  Autonomic motor neurones carry impulses from the CNS to cardiac muscle, smooth
muscle in the gut wall and to glands which are not under voluntary control
 Have cell bodies outside the CNS in autonomic ganglia
 Mostly unmyelinated

Autonomic:
 Preganglionic neurones
o Carry action potentials from the CNS to the
ganglia

2 parts - sympathetic and parasympathetic
 STRUCTURE:
o Sympathetic has short pre-ganglionic neurone
and long post-ganglionic neurone
 Therefore ganglia nearer spinal cord
o Parasympathetic has long pre-ganglionic
neurone and short post-ganglionic neurone
 Therefore ganglia nearer organ
o Sympathetic use noradrenaline
 (as a neurotransmitter at the synapse
between neurone and effector)
o Parasympathetic use acetylcholine
 (as a neurotransmitter at the synapse between neurone and effector)
 ROLES:
o Sympathetic used in stress/fight/flight (gets the body ready for action)
o Parasympathetic used in rest/relaxation/calm
 Sympathetic increases and parasympathetic decreases:
- Heart rate/blood pressure
- Speed/rate/depth of breathing
- Airway diameter
o Sympathetic increases blood flow to skeletal muscle
o Parasympathetic increases blood flow to gut (smooth muscle)
 Sympathetic involved in orgasm
 Parasympathetic involved in sexual arousal
o Sympathetic dilates pupils
o Parasympathetic constricts pupils
 Sympathetic makes liver release glucose
 Parasympathetic makes liver take up glucose
o Sympathetic reduces peristalsis/digestion
o Parasympathetic allows peristalsis/digestion