B9 (all) Flashcards
Describe a nerve impulse
an electrical signal that passes along nerve cells called neurones
Describe the human nervous system
It consists of:
- the central nervous system (CNS) which has the brain and spinal cord
- the peripheral nervous system
- sense organs and effectors, to coordinate and regulate body functions
voluntary and involuntary actions
voluntary actions require a conscious decision to be made
involuntary actions don’t involve conscious decisions so are much faster and produce the same response
Identify from diagrams:
1. motor (effector)
2. relay (connector)
3. sensory neurones
see diagrams in textbook or notebook!
Describe a simple reflex arc
the pathway taken by electrical impulses as they travel along neurones.
describe the reflex arc of someone stepping on a pin
- stimulus: stepping on a pin
- impulse starts at the receptor
- impulse is passed along the sensory neurone
- impulse is passed along the relay neurone
- impulse is passed along the motor neurone
- effector receives impulses to react
- response: lift foot away
basically: stimulus –> receptor –> sensory neurone –> relay neurone in CNS –> motor neurone –> effector –> response
Describe a reflex action
a means of automatically and rapidly INTERGRATING AND COORDINATING STIMULI with the responses of effectors (muscles and glands)
what is a stimulus
a change in conditions
what does a receptor do?
it recognizes the stimulus for a response to occur
what does an effector do?
it carries out the response
what are sensory neurons?
they link sense organs to the CNS
what are relay/connector neurons?
they are short neurons within the CNS
what are motor/effector neurons?
they connect the CNS to an effector such as a muscle
Identify the structures of the eye:
- cornea
- iris
- pupil
- lens
- retina
- optic nerve
- ciliary muscles
- suspensory ligaments
- blind spot
see the diagram and memorize it!!
Describe the function of the cornea
it refracts light
Describe the function of the iris
it controls how much light enters pupil
Describe the function of the lens
it focuses light onto the retina
Describe the function of the retina
it contains LIGHT RECEPTORS, some sensitive to light of different colours
Describe the function of the optic nerve
it carries impulses to the brain
Explain the pupil reflex
In response to the INTENSITY OF LIGHT, CIRCULAR AND RADICAL muscles in the iris work as ANTAGONISTIC PAIRS to dilate or contract the pupil
- bright light: circular muscle contract, radical muscles relax, pupils constrict
- dim light: circular muscle relax, radical muscles contract, pupils dilate
Explain accommodation to view near and distant objects
accommodation is controlled by the CILIARY MUSCLES and the SUSPENSORY LIGAMENTS. accommodation allows us to FOCUS on near or distant objects, and it makes the lens CHANGE SHAPE.
Define a hormone
it is a CHEMICAL SUSBSTANCE produced by a GLAND, carried by the BLOOD. It ALTERS THE ACTIVITY of one or more specific TARGET ORGANS.
Describe adrenaline
It is the hormone secreted in ‘fight or flight’ situations. Its effects are limited to increased breathing and pulse rate and widened pupils.
Situations in which adrenaline secretion increases
examples of these situations are:
- when you’re scared or stressed
- “flight or flight” situations
- in the face of danger
- in exciting situations
Roles of the hormone adrenaline?
- it has CHEMICAL CONTROL OF METABOLIC ACTIVITY. it helps mobilize energy stores in the form of glucose and free fatty acids
- it INCREASES BLOOD GLUCOSE CONCENTRATION. since sugars are stored in the liver as glycogen, the adrenaline triggers the release of glucagon with breaks down glycogen into glucose.
- it INCREASES PULSE RATE. it increases blood circulation of oxygen, and glucose allows cells more respiration for faster muscle contraction
Compare nervous and hormonal control systems
nervous:
1 - electrical impulses are messengers
2 - nerve impulses transmitted through neurons
3 - voluntary + involuntary
4 - localized responses
5 - transmission is fast but short-lived
hormonal:
1 - hormones are chemical messengers
2 - hormones transmitted through blood vessels
3 - involuntary
4 - widespread responses
5 - transmission is slow but last longer
what are the two systems involve in the co-ordination and response in humans?
the nervous system and the hormonal (endocrine) system
Define homeostasis
it is the maintenance of a CONSTANT INTERNAL ENVIORNMENT. homeostasis is the control of internal conditions within set limits.
Control by negative feedback?
This is where a change in a stimulus cause a response that produces the opposite change.
A change is detected by a receptor and an effector is activated to induce an opposite effect.
This promotes equilibrium.
It is designed to prevent large increases or decreases from the best conditions.
Roles of insulin and glucagon from the pancreas? Control of blood-glucose concentrations?
The blood-glucose concentration should remain within a small range because if it rises or falls too much you can become very ill.
After a meal, the blood-glucose concentration rises rapidly
Cells in the pancreas detect this increase and respond by releasing the hormone insulin. It causes any excess glucose to be converted to another carbohydrate, glycogen which is stored in the liver.
Between meals: glucose in the blood is constantly diffusing into cells for use in cellular respiration.
So the blood-glucose concentration falls.
When a low level of glucose is detected by the pancreas, the insulin-secreting cells stop secreting insulin and other cells start to secrete the hormone glucagon instead.
Glucagon converts some of the stored glycogen back into glucose, which is released into the blood to raise the blood-glucose concentration again.
Name and identify on a diagram of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue
see and memorize diagram! be able to label it!
Describe the maintenance of a constant internal body temperature in humans (shivering and brain)
shivering:
RELEASES ENERGY FROM GLUCOSE in respiration; some of this energy is RELEASED AS HEAT to warm us up
brain:
controlled by the HYPOTALAMUS in your brain; if you’re too hot or cold, the brain SENDS NERVE IMPULSES TO THE SKIN
Describe the maintenance of a constant internal body temperature in humans in terms of vasodilation
- arterioles get wider and get closer to the surface of the skin
- the hairs on your skin lay flat
- the blood flow in the capillaries increases and the sweat glands secrete sweat
- the blood in the arterioles transfer heat energy to the sweat, and so when the sweat evaporates, the heat energy is taken with it
- thus more heat is lost from the skin and you cool down
vasodilation = gets cooler
Describe the maintenance of a constant internal body temperature in humans in terms of vasoconstriction
- arterioles get narrower and sink away from the surface of the skin
- blood flow in the capillaries decreases and the hairs on your skin stand up to trap air and create an insulation layer
- so less heat is lost from the skin
vasoconstriction = gets warmer
Define gravitropism
it is a response in which parts of
a plant grow towards or away from gravity
Define phototropism
it is a response in which
parts of a plant grow towards or away from the direction from which light is coming
Explain phototropism + gravitropism of a shoot as examples of the chemical control of plant growth
Certain chemicals in plants regulate plant growth.
In PHOTOTROPISM, these chemicals move to the part of the plant receiving less light. This causes that part of the plant to grow more than the side receiving light, making the plant BEND TOWARDS THE LIGHT.
In GRAVITROPISM, the plant hormone gathers on the lower side of the plant (because of gravity, duh). This makes the shoot CURVE UPWARDS and the root CURVE DOWNWARDS.
How would you investigate gravitropism and phototropism in
shoots and roots?
COMMON SENSE (describe a practical baisically) ex. for phototropism, using a lamp. and for gravitropism, turning the seeds to see the effect of gravity. very easy, not so hard :)
Explain the role of auxin in controlling shoot growth.
– auxin is made in the shoot tip only
– auxin spreads through the plant from the shoot tip
– auxin is unequally distributed in response to light and gravity (so the shoot might bend and curve)
– auxin stimulates cell elongation
