12. Coordination and response Flashcards
CNS and PNS
(a) the central nervous system (CNS) - brain and the spinal cord
(b) the peripheral nervous system (PNS)- nerves outside of the brain and spinal cord
electrical impulses travel along neurones
role of the nervous system
coordination and regulation of body functions
make sense of our surroundings and respond to them
Describe a simple reflex arc
receptor
sensory neurone
relay neurone
motor neurone
effector
Describe a reflex action
a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
Structure and function of a synapse
a junction between two neurons that ensures impulses travel in one direction only
vesicles containing neurotransmitter molecules,
the synaptic gap
receptor proteins
How does an impulse travel from one neurone to the other
(a) an impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap
(b) the neurotransmitter molecules diffuse across the gap
(c) neurotransmitter molecules bind with receptor proteins on the next neurone
(d) an impulse is then stimulated in the next neurone
Describe sense organs
groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
Function of each part of the eye
(a) cornea – refracts light
(b) iris – controls how much light enters the pupil
(c) lens – focuses light on to the retina
(d) retina – contains light receptors, some sensitive to light of different colours
(e) optic nerve – carries impulses to the brain
(f) blind spot- where optic nerve leaves, no receptor cells there
(g) fovea- part of retina where cone cells are tightly packed; this is where light is focused when you look directly at an object.
Pupil reflex
An automatic response to change in light intensity; receptors in retina and effector is the muscles in iris- antagonistic action of circular and radial muscles in the iris
B- circular muscles contract, radial muscles relax, pupil constricts, diameter decreases to prevent too much light entering eye and damaging retina.
D- circular muscles relax, radial muscles contract, pupil dilates, diameter increases to allow as much light into the eye as possible
Accomodation
Changing the shape of the lens to focus on objects at different distances from the eye.
N- CM contract, SL loosened, L thicker, more refraction and diverge
F- CM relax, SL pulled tight, L thin, less refraction & diverge
distribution and function of rods and cones
(a) greater sensitivity of rods for night vision- dim light, less tightly packed further out on retina
(b) three different kinds of cones, absorbing light of different colours, for colour vision- bright light, tightly packed in fovea
Describe a hormone
specific endocrine glands and state the hormones they secrete
a chemical substance, produced by a gland and carried by the blood which alters the activity of one or more specific target organs.
(a) adrenal glands- adrenaline
(b) pancreas- insulin & glucagon
(c) testes- testosterone
(d) ovaries- oestrogen and progesterone
Describe adrenaline and its effects
the hormone secreted in ‘fight or flight’ situations
(a) increased breathing rate- more oxygen can enter blood
(b) increased heart rate- more O2- aerobic respiration- energy for fighting or running away
(c) increased pupil diameter- more light into the eye, see danger more clearly
(d) increased BGC- allows muscles to increase metabolic activity
Compare nervous and hormonal system
made of neurones, info- transmitted in the form of impulse along neurones, travel quickly, effect lasts for a very short time
made of glands, info- transmitted in the form of chemicals called hormones carried in blood plasma, travel slowly, effect lasts for a long time
Describe homeostasis
negative feedback
the maintenance of a constant internal environment.
A mechanism that detects a move away from the set point- (the normal level that the system tries to maintain within a range) and brings about actions that take the value back towards the set point.
