B9 - Coordination and response Flashcards
Two components of the human nervous system
- central nervous system (CNS)
- peripheral nervous system (PNS)
Central nervous system
The brain and the spinal cord
Peripheral nervous system
All of the nerves in the body
Functions of the nervous system (2)
- Makes sense of our surroundings and reponds to them
- Coordinate and regulate body functions
Nerve impulses
Electrical impulses that pass along nerve cells known as neurons which send information through the nervous system
Nerve
A bundle of neurones
Three types of neurons
- Sensory
- Relay
- Motor
Sensory neurone (definition)
Sensory neurones carry impulses from sense organs to the CNS (brain or spinal cord)
Relay neurones (definition)
Relay neurones are found inside the CNS and connect sensory and motor neurones
Motor neurons (definition)
Motor neurones carry impulses from the CNS to effectors (muscles or glands)
Describe and explain the structure of a neuron
- Neurones have a long fibre called an axon
- less time is wasted transferring the impulse from one cell to another
- Axon is insulated by a fatty sheath called a myelin sheath with small uninsulated sections along it called nodes (of ranvier)
- the electrical impulse does not travel down the whole axon but jumps from node to node
- The area over the axon covered by the myelin sheath are schwann cells
- Cell body contains many extensions called dendrites
- means they can connect to many other neurones and recieve impulses from them, forming a network for easy communication
Describe the different structures of three types of 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
Voluntary response
One where you make a conscious decision to carry out a particular action therefore it starts with your brain
* e.g. pick up a cup of coffee
* usually take longer to enact
Involuntary response (reflex)
One that does not involve the brain as the coordinator of the reaction and you are not aware you have completed it until after you have carried it out
* basic instincts for survival, are quicker than any other type of nervous response
* help minimise damage to the body
The reflex pathway (6)
- The stimulus is detected by a pain/pressure/touch receptor in the skin
- Sensory neurone sends electrical impulses to the spinal cord (the coordinator)
- Electrical impulse is passed on to relay neurone in the spinal cord
* Relay neurone connects to motor neurone and passes the impulse on
* Motor neurone carries impulse to a muscle in the leg (the effector)
* The muscle will contract and pull the foot up and away from the sharp object (the response)
Synapses (function and definition)
Where two neurons meet or join, they do so at a junction called a synapse
* improtant in the nervous system being a connected network of neurones
* can transmit nerve impulses and direct them along the appropriate route
Receptors
A group of specialised cells that detect a change in the environment and stimulate electrical impluses in response
Sense organs (definition and 5 examples)
Contain groups of receptors that respond to specific stimuli
* skin
* tongue
* nose
* ear
* eye
Skin (sense and sensitivity
Touch and temperature
* sensitive to pressure, heat and cold (temperature) and pain
Tongue (sense and sensitivity)
Taste
* sensitive to chemicals in food and drink
Nose (sense and sensitivity)
Smell
* sensitive to chemicals in the air
Ear (sense and sensitivity)
Hearing and balance
* sensitive to sound and movement
Eye (sense and sensitivity)
Sight
* sensitive to light
Eye (definiton)
The eye is a sense organ containing receptor cells that are sensitive to light (rod cells) and colour (cone cells)
Cornea
Transparent lens that refracts light as it enters the eye
Iris
Controls how much light enters the pupil
Lens
Transparent disc that can change shape to focus light onto retina
Retina
Contains light receptor cells - rods (detect light intensity) and cones (detect colour)
Optic nerve
Sensory neurone that carries impulses between the eye and the brain
Pupil
Hole that allow light to enter eye
Blind spot
At the point where the optic nerve joins the retina, there are no light-sensitive rod and cone cells on that part of the retina
* will not result in an image being detected
* brain fills in from surrounding light so we don’t see a black hole
Pupil reflex
This is a reflex action carried out to protect the retina from damage in bright light and protect us from not seeing objects in dim light
Antagonistic muscle action in the pupil reflex
The muscles that work antagonistically are the radial muscles and the circular muscles of the eye
* when one set contracts, the other relaxes
How does the eye respond to dim light? (5 steps)
- Photoreceptors detect change in environment (dark)
- Radial muscles contract
- Circular muscles relax
- Pupil dilates (diameter widens) to allow more light to enter the eye and improve vision
- More light enters the eye
How does the eye respond to bright light? (5 steps)
- Photoreceptors detect change in environment (bright)
- Radial muscles relax
- Circular muscles contract
- Pupil constricts (diameter narrows) to protect retina from damage
- Less light enters the eye
Radial muscles
Outer muscles of the retina which point inward towards the pupil
Circular muscles
Inner muscles of the retina which surround the pupil and are circular shaped
Responses to dark light (radial and circular muscles, pupil size and amount of light)
- Radial muscles: contract
- Circular muscles: relax
- Pupil size: wide
- Light amount: more
Responses to bright light (radial and circular muscles, pupil size and amount of light)
- Radial muscles: relax
- Circular muscles: contract
- Pupil size: narrow
- Light amount: less
Accomodation
The function of the eye in focusing on near and distant objects
What changes to accomodate object distance and focus?
- The elastic lens’ shape can be changed by the tightness or looseness of the suspensory ligaments
- this change is brought upon by the contraction or relaxation of the ciliary muscles
How does the eye respond when an object is close up? (4 steps)
- 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
How does the eye respond when an object is close up? (4 steps)
- 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
Far away object response (ciliary muscles, suspensory ligaments, lens)
- Ciliary muscle: relaxed
- Suspensory ligament: pulled tight
- Lens: thinner
Close up object response (ciliary muscles, suspensory ligaments, lens)
- Ciliary muscle: contracted
- Suspensory ligament: slack
- Lens: fatter
Hormone (definition and function)
A chemical substance produced by a gland and carried by the blood
* the alter the activity of one or more specific target organs - chemicals which transmit information from one part of the organism to another and bring about a change
Endocrine system
The glands that produce hormones in animals
* have good blood supply as they need to get hormones into the blood stream (plasma)
Function of the liver in terms of hormones
Regulates levels of hormones in the blood: transforming or breaking down any that are in excess
Adrenaline (source, role, effect)
- Source: adrenal gland
- Role: readier the body for a ‘fight or flight’ response
- Effect: increases heart and breathing rate, dilates pupils
Insulin (source, role, effect)
- Source: pancreas
- Role: lowers blood glucose levels
- Effect: causes excess glucose in the blood to be taken up by the muscles and liver and converted into glycogen for storage
Testosterone (source, role, effect)
- Source: testes
- Role: main sex hormone in males
- Effect: development of secondary sexual characteristics in males
Oestrogen (source, role, effect)
- Source: ovaries
- Role: main sex hormone in females
- Effect: development of secondary sexual characteristics in females and controls menstrual cycle
Thyroid glands
Thyroxine
Pituitary gland
The ‘master gland’ situated at the base of the brain
Comapre composition of nervous system and endocrine system
- Nervous: nerves (neurones), brain, spinal cord
- Endocrine: glands
Compare message type in nervous and endocrine system
- Nervous: electrical impulses
- Endocrine: chemical hormone
Compare speed of transmission in nervous and endocrine system
- Nervous: very fast
- Endocrine: slower
Compare the length of effect in nervous and endocrine system
- Nervous: short - until nerve impulses slow
- Endocrine: longer - until hormone is broken down
Flight
remove oneself rapidly from a dangerous situation
* eg. run away
Fight
if flight is not possible, resort to physical combat to overcome danger
Effects of adrenalin (name 3 in depth)
- Increasing pulse rate and breathing rate: oxygen and glucose can be delivered to muscle cells and carbon dioxide taken away from muscle cells more quickly
- Increasing blood glucose concentration for increased respiration in muscle cells
-
Diverting blood flow towards muscles and away from non-essential parts of the body like alimentary canal
- to ensure the reactants of respiration are as available as possible
-
Dilating pupils: allow as much light as possible to reach the retina
- more information can be sent to the brain
Homeostasis
Homeostasis is defined as the maintenance of a constant internal environment
* internal conditions within the body need to be kept within set limits in order to ensure that reactions in body cells can function
* if one condition deviates, the body will not function properly and without medical intervention this can lead to death
What happens if glucose levels are too high in the body?
Usually directly after a meal glucose levels are high
* The kidneys can only cope with a certain level in the blood
* If level gets too high, glucose gets excreted and lost in the urine
How does insulin help with glucose levels?
- Insulin temporarily converts excess glucose into glycogen in the liver and muscles
- it decreases blood glucose concetration
- Hours later glycogen is converted back to glucose once levels have dipped due to respiration in all tissue
Negative feedback (definition and behaviour)
Negative feedback occurs when conditions change from the ideal or set point and returns conditions to this set point (called the normal)
* Behaviour:
* if the level of something rises, control systems are switched on to reduce it again
* if the level of something falls, control systems are switched on to raise it
Negative feedback cycle
- Conditions in the body change from set point
- Change detected
- Corrective mechanisms activated
- Conditions return to set point
- Corrective mechanism switched off
How are blood glucose levels controlled?
By negative feedback mechanism involving insulin and glucagon both of which are made in the pancreas
Difference between the use of insulin and glucagon
- Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored
- Glucagon is produced when blood glucose falls and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the blood
Type 1 diabetes
A condition where the blood glucose levels are not able to be regulated as the insulin-secreting cells in the pancreas are not able to produce insulin
Structure of the skin
Fatty tissue function
Fatty tissue under the dermis acts as a layer of insulation to prevent too much body heat being lost through the skin
Homeostatic process in response to an increase in body temperature (5 steps)
- Increase in body temperature (above 37 degrees)
- Thermoreceptors in the hypothalamus and skin detect change
- Possible changes:
- increase sweating
- vasodilation
- hairs lie flat against skin
- Decrease in body temperature
- Normal body temperature
Homeostatic process in response to a decrease in body temperature (5 steps)
- Decrease in body temperature (above 37 degrees)
- Thermoreceptors in the hypothalamus and skin detect change
- Possible changes:
- shivering
- vosoconstriction
- hairs lie erect
- Increase in body temperature
- Normal body temperature
Homeostasis when we are hot (2 possible steps)
-
Sweat is secreted by sweat glands
- this cools skin by evaporation: heat energy from the body is lost as liquid water in sweat becomes water vapour
-
Hairs lie flat against the skin allowing air to freely circulate
- this increases heat transfer to the environment by radiation
Homeostasis when we are cold (2 possible processes)
- Skeletal muscles contract rapidly and we shiver
- involuntary muscle contractions need energy from respiration and some of this is released as heat
- Erect hairs trap a layer of air around the skin which acts as an insulator, preventing heat loss by radiation
Vasoconstriction
When we are cold blood flow in capillaries slows down because arterioles leading to the skin capillaries get narrower
* this reduces the amount of heat lost from blood by radiation as less blood flows through skin surface
Vasodilation
When we are hot, blood flow in capillaries increases because blood vessels to the skin capillaries get wider
* this cools the body as blood is flowing at a faster rate through skin surface and more heat is lost by radiation
Positive response
Plants grow towards the stimuli
Negative response
Plants grow away from the stimuli
Describe the tropism of gravity (name, def, pos. and neg. response)
- Name: gravitropism
- Def: growth towards or away from gravity
- Pos. response: growth towards gravity (e.g. roots)
- Neg response: growth away from gravity (e.g. shoots)
Describe the tropism of light (name, def, pos. and neg. response)
- Name: phototropism
- Def: growth towards or away from the direction of light
- Pos. response: growth towards light (e.g. shoots)
- Neg response: growth away from light (e.g. roots)
Explain shoot phototropism
Shoots must grow upwards, away from gravity and towards light, so that leaves are able to absorb sunlight
Explain root gravitropism
Roots need to grow downwards into the soil, away from light and towards gravity, in order to anchor the plant and absorb water and minerals from the soil particles.
Investigation for phototropism (set-up)
- Set up three light proof boxes with identical plants in each
- Box A: unilateral light from a small opening
- Box B: unilaterial light from a small opening and a clinostat (rotating apparatus) into which the plant is placed
- Box C: a fully light proof box
Investigation for phototropism (results)
- The seedlings in A grow towards the light source
- In B the effect of the light only coming from one direction has been cancelled out by using a clinostat (it revolves slowly and repeatedly, so the shoots are evenly exposed to light)
- this means all sides of the seedlings get an equal amount of light so they do not curve towards the light source but grow straight up
- In C the seedlings grow straight up for light and the plant becomes tall and slender with yellowing leaves due to the lack of light
Investigating gravotropism (set-up)
- Add some damp cotton wool to two petri dishes
- Place 3 bean seedling in the cotton in each dish
- Dish A - radicle facing downwards
- Dish B - horizontally
- Dish C - facing upwards
- Cover each dish with a lid
- Attach B to a support so that it’s on its side
- Attach C to a clinostata
- Place both in a light proof box and leave for two days
Investigating gravotropism (result)
- Dish B: radicles have grown downwards (positive gravitropic response) and all plumules have grown upwards (negative gravitrophic response)
- Dish C: all plumules have grown neither up nor down but straight outwards in whichever direction they were placed
* the effect of gravity has been cancelled out by the revolving of the clinostat - they have shown no gravitropic response at all
Why did the gravitropism experiment have to be done in a lightproof box?
To cancel out the effect of light on the growth of the seedlings
Auxin
A growth hormone called auxin controls the direction of growth of roots or stems
* plants use this to respond to stimuli
Where is auxin made?
Mostly made in the tips of the growing stems and roots
* can diffuse to other parts by spreading from a high concentration in the shoot tips down the shoot to lower concentrated areas
What does auxin do to the plant?
Stimulates cells behind the tip to elongate
* the more auxin there is, the faster they will elongate and grow
* therefore, only the region behind the tip of a shoot (meristem) is able to contributo to growth
How does auxin respond when light shines on the tip?
Auxin is distributed evenly throughout the cell and the cells in the meristem grow at the same time
How does auxin respond when light shines predomenantly from one side?
Auxin concentrates on the shaded side making the cells on that side elongate and grow faster than the cells on the sunny side
* unequal growth causes the shoot to bend and grow in the direction of the light
Negative geotropism
When shoots grow away from gravity it is known as negative geotropism
* Gravity modifies the distribution of auxin so that it accumulates on the lower side of the shoot
Positive geotropism
When roots grow towards gravity it is known as positive geotropism
* In roots, higher concentrations of auxin results in a lower rate of cell elongation
