14: Coordination and response Flashcards
Where do electrical impulses travel?
Along neurones
What does the central nervous system (CNS) consist of?
The brain and the spinal cord
What does the peripheral nervous system (PNS) consist of?
The nerves OUTSIDE the brain & spinal cord
Describe the role of the nervous system
Coordination and regulation of body functions
Identify sensory, relay & motor neurones
- Sensory neurones are long and have a cell body branching off the middle of the axon
- Relay neurones are short and have a small cell body at one end with many dendrites branching off it
- Motor neurones are long and have a large cell body at one end with long dendrites branching off it
Describe a simple reflex arc
stimulus –> receptor –> sensory neurone –> relay neurone –> motor neurone –> effector –> response
Describe a reflex action
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
What is a synapse?
A junction between two neurones
Describe the structure of the synapse
- the presence of vesicles containing neurotransmitter molecules
- the synaptic gap
- receptor proteins
Describe events at a synapse
- the impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap
- the neurotransmitter molecules diffuse across the gap
- neurotransmitter molecules bind with receptor proteins on the next neurone
- an impulse is then stimulated in the next neurone
Which direction do synapses travel in?
They only travel is ONE direction
Describe sense organs
Groups of receptor cells responding to specific stimuli: light, sound, touch, temperature & chemicals
Function of the cornea
Refracts light
Function of the iris
Controls how much light enters the pupil
Function of lens
Focuses light on to the retina
Function of retina
Contains light receptors, some sensitive to light of different colours
Function of optic nerve
Carries impulses to the brain
What is the pupil reflex?
- dim light the pupil dilates (widens) in order to allow as much light into the eye as possible
- bright light the pupil constricts (narrows) in order to prevent too much light entering the eye and damaging the retina
What is the pupil reflex in terms of antagonistic action?
DARK –> radial contract, circular relax, wide pupils, more light enters
BRIGHT –> radial relax, circular contract, narrow pupils, less light enters
Explain accomodation to view near objects
The ciliary muscles contract (the ring of muscle decreases in diameter)
This causes the suspensory ligaments to loosen
This stops the suspensory ligaments from pulling on the lens, which allows the lens to become fatter
Light is refracted more
Explain accomodation to view distant objects
The ciliary muscles relax (the ring of muscle increases in diameter)
This causes the suspensory ligaments to tighten
The suspensory ligaments pull on the lens, causing it to become thinner
Light is refracted less
Describe distribution of rods and cones in the retina of a human
Rods = all over the cells (other than the area where the optic nerve attaches to the retina)
Cones = in the blind spot
Function of rods
Greater sensitivity of rods for NIGHT VISION
Function of cones
3 diff types of cones
- absorbs ligth of different colours for colour vision
Describe a 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 glands secrete which hormone?
Adrenaline
The pancreas secretes which hormone?
Insulin and glucagon
Testes secrete which hormone?
testosterone
Ovaries secrete which hormone?
Oestrogen
Describe adrenaline & what happens
The hormone secreted in ‘fight or flight’ situations and its effects are:
- increased breathing rate
- increased heart rate
- increased pupil diameter
How does adrenaline affect the metabolic activity?
- increases the blood glucose concentration
- increases heart rate
Difference between nervous & endocrine system
- what it contains
- what it moves
- speed
- length of effect
nervous: nerves, brain, spinal cord | endocrine: glands
nervous: electrical impulse | endocrine: chemical hormone
nervous: speed - very fast | endocrine: speed - slower
nervous: length of effect = short (until nerve impulses stop)| length of effect = longer (until hormone is broken down)
Describe homeostasis
the maintenance of a constant internal envionrment
How does insulin affect blood glucose concentration?
It decreases it
What is negative feedback
It is the concept of homeostatic control with a reference to a set point
How does negative feedback work?
If a factor (e.g. blood glucose or temperature) INCREASE, the body’s response is to make it DECREASE
…vise versa
Describe the control of blood glucose concentration in the liver
1. role of insulin
Insulin = secreted when HIGH sugar blood levels, stimulates liver cells to convert glucose –> glycogen
- levels FALL
Describe the control of blood glucose concentration in the liver
1. role of glucagon
Glucagon - secreted when LOW blood sugar levels, stimulates liver cells to convert glycogen into glucose
- levels INCREASE
Treatment of Type 1 diabetes
Type 1 diabetes = blood glucose levels are not able to be regulated as the insulin-secreting cells in the pancreas are not able to produce insulin
BLOOD GLUCOSE LEVELS ARE OFTEN TOO HIGH!!
Treatment = injecting insulin
extra insulin causes the liver to convert GLUCOSE INTO GLYCOGEN, which REDUCES the blood glucose level
How do you maintain a constant internal body temperature in mammals?
Insulation, sweating, shivering & the role of the brain
How do you maintain a constant internal body temperature in mammals?
vasodilation & vasoconstriction of arterioles supplying skin surface capilliaries
Describe gravitropism
a response in which parts of the plant grow towards or away from GRAVITY
Describe phototropism
a response in which parts of a plant grow towards or away from THE DIRECTION OF THE LIGHT SOURCE
Explain role of auxin in controlling shoot growth
- auxin is made in the shoot tip
- auxin diffuses through the plant from the shoot tip
- auxin is unequally distributed in response to light & gravity
- auxin stimulates cell elongation
Explain role of auxin in controlling shoot growth
- auxin is made in the shoot tip
- auxin diffuses through the plant from the shoot tip
- auxin is unequally distributed in response to light & gravity
- auxin stimulates cell elongation
