6 Coordination And Response Flashcards
Receptor
Receives / detects the stimulus
Coordinator
Determines the response
Effector
Carries out the response
Together the brain and spinal chord are known as the …
Central nervous system
Iris
Controls how much light enters the eye
Pupil
Space in the iris through which light passes
Cornea
Transparent front part of the eye that causes some bending of light
Conjunctiva
Thin transparent protective outer covering that helps prevent the entry of microorganisms
Retina
Layer of light sensitive cells that can sense different coloured light as well as cells that don’t sense colour at all
Lens
Refracts light to obtain a focused image
Optic nerve
A bundle of neurons that carries impulses from the retina to the brain
Eye focused on a distant object:
- ciliary muscles relax
- suspensory ligaments pulled tight
- lens pulled thin
Eyes focused on nearby object:
- ciliary muscles contract
- suspensory ligaments slackened
- lens allowed to bulge
Adaptions of the nerve cells: (3)
Long length - to carry impulses long distances Insulating sheath - to allow rapid transmission of impulses Branching ends (dendrites) - to receive or pass impulses from or to many other nerve cells
What happens when an impulse reaches a synapse: (6)
- The impulse reaches the synaptic bulb (the end of the neurone)
- vesicles containing the transmitter move towards the cell membrane at the synapse by diffusion
- vesicles release their neurotransmitter into the gap between the two cells
- neurotransmitter diffuses across the gap
- the neurotransmitter reaches the membrane of the next cell
- when enough neurotransmitter reaches the next cell an impulse will occur
Voluntary actions
Actions which we have conscious control over
Reflex actions
Unconscious actions which tend to be much faster as they use the reflex arc to do away with “thinking time”. Used as a means of protection.
Order of reflex arc
- pain receptor
- sensory neurone
- into spinal nerve
- impulses across relay neurone
- impulses across motor neurone
- message from motor neurone makes muscle contract
Low levels of glucose:
- Normal levels of glucose in blood
- Insulin not produced by the pancreas
- Less glucose absorbed by body cells
- Blood glucose remains the same
High levels of glucose
Too much glucose in blood
Pancreas produces insulin which enters the blood
Insulin allows glucose to be absorbed by body cells
Blood glucose reduced
Which organ does insulin travel to?
The liver
How do the cells of the liver respond to insulin?
- increasing their uptake of glucose
- increasing their respiratory rate
- converting glucose into glycogen for storage
What is the mechanism that insulin uses to control blood glucose levels?
Negative feedback
What is diabetes ?
The condition where people fail to produce enough insulin or fail to respond to it correctly
Symptoms of diabetes (3)
Lethargy
Excessive thirst
Glucose in the urine
Long term dangers of untreated diabetes (3)
Kidney damage
Eye damage
Heart disease
Roles of the kidney (2)
Filter out toxins
Regulate concentration of blood “Osmoregulation”
What does ADH allow the kidneys to do?
In the kidneys the ADH allows the medulla of the kidney to reabsorb more water into the blood
Drinking large volume of water (5)
- Blood more dilute than normal
- brain
- less ADH released
- less water reabsorbed by kidneys
- large volume of dilute urine produced
How bending in a shoot is brought about if it is exposed to light from one side (6)
- auxin is produced by the tip of the shoot
- the auxin diffuses away from the shoot tip
- if light is receive from one side the auxin is found in higher concentrations on the shaded side
- auxin causes cells to elongate
- the cells on the shaded side become longer than those on the illuminated side
- the shoot bends towards the light
ADH and urine production - hot day
- Exercise in hot conditions
- Blood more concentrated than normal (contains less water)
- Brain
- more ADH released
- More water absorbed by kidneys
- Low volume of concentrated urine produced
Motor neurone
Carries instructions from the CNS to the effector
Neuromuscular junction
Synapse between motor neurone and muscle
Give examples of a reflex action and explain how they work
The knee jerk - a light tap on lower patella tendon causes upper thigh muscle to stretch
Ankle kick - the ankle kicks back as the calf contracts
What is the knee jerk’s use to the body?
Keeps the walk co-ordinated
The knee jerk is described as a monosynaptic spinal reflex. What does this mean?
The impulse travels through the spinal chord and back to the knee
How do the stretch receptors in our muscles help to maintain our posture when we are standing up ?
They keep you standing up straight if you begin to tip to one side
Why would a poison that blocked the action of acetyl chloine interfere with the control of our muscles ?
It would block transmissions across the synapse
Travel of an impulse :
- Sensory neurone
- Association neurone
- Motor neurone
When light becomes dim
The pupil would dilute to allow more light to enter the eye and form an image
Layers of the kidney:
Outer layer - cortex
Branch of the aorta into the kidney - renal artery
Useful substances are reabsorbed - Medulla
Top of the kidney - Adrenal gland
Out of the kidney - renal vein
Stems into the medulla - Ureter
Differences between the nervous system and hormonal system(2)
- Hormones target organs in order to produce temporary changes in the way cells function
- Neurone are specially adapted to rapidly carry electrical impulses through the nervous system for instant, unconscious actions (reflexes) and conscious actions
What is the basic structure of the CNS
The brain and spinal cord together form the CNS that controls and co-ordinates the responses between the receptors and effectors and muscles
Changes in the eyes if the light is dim (2)
- Pupil will dilate to allow more light in to form an image
- Lens refracts light to obtain a focused image
What is the aim of hormones?
To maintain an constant internal environment for the proper functioning of cells and enzymes in response to internal and external change
What is negative feedback? (3)
- insulin uses negative feedback to control blood glucose levels
- The Action of insulin reducing blood glucose levels means that less insulin is needed
- When normal blood glucose levels are restored the pancreas will no longer need to release insulin
When does type 1 diabetes occur?
Usually occurs early in life when the pancreas stops producing insulin, which then has to be taken as medication throughout life
When does type 2 diabetes occur ?
It is a progressive disease linked to lifestyle factors and obesity when the pancreas gradually produces less insulin, which in early stages means it can be controlled by diet but may need insulin injections
Dim light eye reaction (2)
- Radial muscles of the iris contract
- dilated pupil to let more light in
Cornea and lens reaction to distant object (3)
Light rays arrive parallel
Cornea refracts light
Lens is thin as little additional refraction is necessary to focus light on retina
Lens and cornea reaction to nearby object
- Light Rays diverging
- Cornea refracts light
- Lens is thicker than usual as additional refraction is necessary to focus light on retina
