coordination and response Flashcards
stimulus definition
a change in the environment that can be detected by an organism
the human nervous system consists of:
- The CNS (central nervous system)
- The PNS (peripheral nervous system)
what is the CNS composed of and what does it do?
- Composed of:
- brain and spinal cord- Responsible for coordinating all reactions and nervous communication around the body
what is the PNS composed of and what does it do?
- Composed of:
- Nerves in the other parts- Responsible for transmitting the impulses from the CNS to all parts of the body
3 main types of neurons
- sensory neurone
- motor neurone
- relay neurone
sensory neurone
- Transfer nerve impulses from receptor cells to the spinal cord when a stimulus is detected.
motor neurone
- Transfer nerve impulses from the brain or spinal cord to effectors (such as muscles)
relay neurone
- Connect one neuron to the next
- Found in the brain
- Make links between the sensory neurons and the motor neurons in the spinal cord
synapse
- Junction between two neurons
- Allows an impulse to travel from an axon terminal of one neuron to a dendrite in another neuron
how do synapses work?
- Axon terminals contain tiny, bubble-like structures called vesicles
- Vesicles contain substances called neurotransmitters
- Receptor molecules in dendrites bind to neurotransmitters
how do neurotransmitters travel across the synaptic cleft/synaptic gap?
by diffusion
characteristics of reflex actions
- Rapid
- Automatic
- Innate (you don’t need to learn how to do them)
what is the reflex arc?
- The pathway through the body that brings about a reflex action
- receptor → sensory neurone → relay neurone → motor neurone → effector
receptor cells
- Cells that detect different stimuli
Include:
- Touch receptors in the skin
- Sound receptors in the ear
- Light receptors in the eye
- Taste (chemical) receptors in the nose, tongue and mouth
- Temperature receptors in the skin and brain
effectors
- Produce a response
Eg. A muscle or a gland that produces a hormone
sense organ
group of receptor cells that respond to a specific stimulus
Light entering the eye travels in this direction:
- cornea → pupil → lens → optic nerve
cornea function
refracts light, focusing it towards the retina
lens function
refracts light, focusing it onto the retina
iris function
controls the amount of light passing through the pupil
retina function
responds to light levels and to light of different colors
optic nerve function
carries nerve impulses from the retina to the brain
in dim light…
- Pupil dilates
- Radial muscles contract
- Circular muscles relax
in bright light…
- Pupil constricts
- Radial muscles relax
- Circular muscles contract
ciliary muscles function
- Control the shape of the lens
- Attached to the lens by suspensory ligaments
To focus light from distant objects onto the retina:
- Ciliary muscles relax
- Tension in suspensory ligaments increases
- Lens becomes thinner
- Light is refracted less strongly
To focus light from near objects onto the retina:
- Ciliary muscles contract
- Tension in suspensory ligaments decreases
- Lens becomes thicker
- Light is refracted more strongly
where are cones located
on the fovea
what do cones provide?
colour vision
3 types of cones:
- red
- blue
- green
where are rods distributed?
mostly around the sides of the retina
what do rods provide?
vision in dim light
hormones (4 points)
- Chemical substance produced by glands
- Transported in the blood
- Alters the activity of one or more specific target organs
- Endocrine system: series of glands that make hormones
the adrenal gland produces…
adrenaline
the pancreas produces..
insulin and glucagon
the ovary produces
oestrogen
the testis produces…
testosterone
effect of insulin and what it causes
- Effect of lowering blood glucose concentration
- Causes cells in the liver to remove glucose from the blood and store it as glycogen
How does Insulin lower blood glucose concentration?
insulin stimulates cells in the liver and tissues such as muscles to use glucose from the blood either to use it for respiration or to store it as glycogen
what does glucagon stimulate?
- Stimulates the breakdown of stored glycogen, releasing more glucose into the blood
what does adrenaline cause?
- Increased breathing rate
- Increased pulse rate
- Widened pupils in the eyes
homeostasis definition
- Maintenance of a constant internal environment within the body
what does homeostasis control?
- Body temperature
- Concentration of glucose in the blood
- Water levels
negative feedback definition
response which is the reverse to the change detected so that levels can return to normal.
eg, when it is cold you start to shiver, which increases again your body temperature
thermoregulation meaning
process that allows the body to maintain a constant core temperature
vasodilation
the widening of blood vessels that causes more blood to flow in the skin capillaries, so more heat is lost from the body
Vasodilation = heat loss
vasoconstriction
the narrowing of blood vessels that causes less blood to flow in the skin capillaries, so less heat is lost from the body
Vasoconstriction = less heat loss
what is meant by type 1 diabetes
- Pancreas does not make enough insulin
- Meaning the glucose in the blood cannot enter cells and is not converted into glycogen
type 1 diabetes symptoms
- Frequent urination (body is trying to secrete excess glucose)
- Increased thirst (due to frequent urination)
tropism definition
a response by a plant to a stimulus
geotropism
a response in which parts of a plant grow towards or away from gravity
phototropism
a response in which a plant grows towards or away from light
what do auxins do?
plant hormone that cause tropisms
