Coordination and response Flashcards
Electrical impulses travel along
neurones
Mammalian nervous system consist of
The central nervous system (CNS) consisting of the brain and the spinal cord
The peripheral nervous system (PNS) consisting of the nerves outside of the
brain and spinal cord.
Role of the nervous system is
coordination and regulation of body functions.
Reflex arc:
receptors detect stimulus and generate impulse, it travels to sensory
neurone, then relay neurone, then to motor neutron, then to the effector.
A reflex action
a means of automatically and rapidly integrating and coordinating
stimuli with the responses of effectors (muscles and glands).
synapse
A junction between two neurones
Structure of synapse include:
presence of vesicles containing neurotransmitter molecules
Synaptic gap/cleft
receptor protein
Events at a synapse:
An impulse stimulates the release of neurotransmitter molecules from vesicles
into the synaptic gap.
The neurotransmitter molecules move from their region of higher concentration to their region of lower concentration down their concentration gradient across the gap
Neurotransmitter molecules bind with receptor proteins on the next neuron
An impulse is then stimulated in the next neuron.
Synapses ensure that
impulses travel in one direction only.
Sense organs
groups of receptor cells responding to specific stimuli: light,
sound, touch, temperature and chemicals.
cornea function
refracts light
iris function
controls how much light enters the pupil
lens function
focuses light on to the retina
retina function
contains light receptors, some sensitive to light of different colours
optic nerve function
carries impulses to the brain
As light intensity increase,
diameter of pupil decrease so that less light enters the
eye and prevent damage. The antagonistic muscles, circular muscles contract and
radial muscles relax.
As light intensity decrease,
diameter of the pupil increase so that more light enters the
eye and prevents damage. The antagonistic muscles, circular muscles relax and
radial muscles contract.
Distant object
Ciliary muscles relax, suspensory ligament pulled tight (tension on
suspensory ligament increase). the lens becomes thin/ less convex.
Near object:
Ciliary muscles contract, suspensory ligament slackened (tension on
suspensory ligament decrease). the lens becomes thick/ more convex.
There are three different kinds of cone cells
red, green and blue
Fovea is almost entirely cones,
packed tightly together
Rods
are found further out
on the retina and are less tightly packed.
Rod cells are more sensitive at night
hormone
a chemical substance, produced by a gland and carried by the blood,
which alters the activity of one or more specific target organs.
Adrenal gland secrete
adrenaline.
Pancreas secrete
insulin and glucagon
Testes
secrete
testosterone
Ovaries secrete
estrogen
Effect of adrenaline:
increased breathing rate
increased heart rate
increased pupil diameter
increase in blood glucose concentration
Speed of action of nervous system is faster than
hormonal control system. Duration
of effect of hormonal control system is longer than the nervous system
Homeostasis
maintenance of a constant internal environment
Insulin decreases
blood glucose concentration.
In negative feedback:
There is a set point – a normal level that the system tries to maintain.
There is a ‘measuring device’ that keeps track of whether the level is within the
range of the set point.
If the level goes outside the set point, this triggers events to happen that bring
the level back into line again.
If blood glucose concentration is too high
it is detected by the pancreas, pancreas
release insulin, insulin stimulate liver cells to absorb glucose from blood across the
partially permeable membrane. Liver cells convert glucose to glycogen and store
glycogen in liver cells, this results in reduction of blood glucose concentration until it
reaches the set, normal point.
If blood glucose concentration is too low
it is detected by the pancreas, pancreas
release glucagon, glucagon stimulate liver cells to convert store glycogen into
glucose, and release this glucose into the blood. This results in increase of blood
glucose concentration until it reaches the set, normal point.
Treatment of type 1 diabetes:
-insulin ;
-by injection / insulin pump ;
- regular blood glucose tests
regular meals and controlled diet
If the internal temperature is above normal
it is detected by the brain. Vasodilation of
arterioles occur, more blood flows to the skin, so more heat is lost form the blood,
decreasing the internal temperature. Sweating occurs which gives a cooling effect
and decreases the internal body temperature
If the internal temperature is below normal
it is detected by the brain.
Vasoconstriction of arterioles occur, less blood flows to the skin, so less heat is lost
form the blood, increasing the internal temperature. Adipose tissue in skin act as
insulation and reduce heat loss. Shivering produce heat and help to keep the body
warm.
Gravitropism
a response in which parts of a plant grow towards or away from
gravity.
Phototropism
response in which parts of a plant grow towards or away from the
direction of the light source
examples of the chemical control of
plant growth
Phototropism and gravitropism
How auxin work:
auxin is made in the shoot tip
auxin diffuses through the plant from the shoot tip
auxin is unequally distributed in response to light and gravity
auxin stimulates cell elongation
