2J (Co-ordination and response) Flashcards
STIMULI
Change in environment
RECEPTOR
Specialised cells that detect changes in environment
E.g, Sensory Neurones in the finger detect heat
EFFECTOR
Part of body that carries out response to Stimuli
E.g Muscles in finger that contract to pull finger away from heat
Sensitivity in organisms:
- All living organisms need to respond to changes in environment for survival
- Nervous system coordinated by the brain allows body to respond to changes in environment
- Organisms additionally have reflexes for fast involuntary actions that protect body from damage
Homeostasis definition
Maintenance of constant water level in body
Examples of homeostasis:
- Osmoregulation
- Thermoregulation
Osmoregulation
- Maintenance of constant water level in the body
Thermoregulation
- Maintenance of optimum body temperature for optimum enzyme activity
- Decreased body temperature –> shivering, vasoconstriction –> will increase body temp to normal (37)
- Increased body temp –> increased sweating, vasodilation –> will decrease body temp to normal (37º)
Coordinated response definition
Process in which a reaction is carried out in response to a change in environment (stimuli)
Do plants respond to stimuli?
Plants are living organisms and therefore respond to change in environment (stimuli) for survival. E.g. Abiotic factors (light, water…) and biotic facotrs (predators, diseases…)
Geotropic response
Growth in response to direction of gravity
Phototopic response
Growth in response to direction of light
2.84
explan in stem and roots
Auxins
- Plant hormone produced in the tip of stem and roots which control the direction of growth
- Auxin changes the elasticity of cells to alter the growth of cells, therefore changing the direction of growth (increase in elasticity will allow cell to absorb more Water, causing size of cell to increase and bend towards specific direction)
- Factors including light and gravity can alter the distribution of Auxin within stem and root, causing different responses
Nervous communication
Nervous system comprising a network of nerve cells that carry impulses between parts of body
Hormonal communication
Endocrine system comprising glands that produce and secrete Hormones to stimulate change in the body
Diferences between nervous and hormonal communication
- Nervous communication is electrical, while Hormonal communication is chemical
- Nervous Communication is faster, while Hormonal communication is slower
- Nervous communication is short - lived, while Hormonal communication is long - lived
Central nervous system
Nervous system comprising the Brain and Spinal Cord that is linked to a network of nerve cells that carry impulses around the body
Process of CNS
- Central Nervous System (CNS) determines the response for a stimulus detected by the receptor
- Stimuli is detected by receptors, stimulating Sensory Neurons that send electrical impulses to the - —Central Nervous System - Brain and Spinal cord
- Central Nervous System relays impulse across the synpase (gaps between Neurones) to Relay Neurons via synaptic transmission
- Relay Neurons relays impulse to Motor Neurons in the Effector, which will quickly carry out rapid response
Synapse
- Junction that separates Neurons from other cells (other Neurons and Receptor or Effector cells)
- As electrical impulses cannot pass across the Synapse, Neurons transmit information across by converting the electrical signal into a chemical signal called Neurotransmitters
Neurotransmitters
Chemical messengers that are released from Neurons to transmit signals across the Synapse
Role of neurotransmitters
- When an electrical impulse reaches the end of an Axon on pre-synaptic Neuron, this triggers the release of chemical messengers called Neurotransmitters via exocytosis
- Neurotransmitter will diffuse across the Synapse and bind to receptors on the membrane of the post-synaptic Neuron
- As a result, post-synaptic Neuron continues to transmit electrical impulse along Axon of Neuron
Reflex
Fast involuntary reaction that protects body from damage
WITHDRAWAL OF FINGER FROM HOT OBJECT:
- When Hand is near a hot object, heat (stimuli) is detected by the Finger (receptor), stimulating Sensory Neurons to send electrical impulses to the Central Nervous System - Brain and Spinal Cord
- Central Nervous System will receive and interpret message, determining the appropriate reaction of pulling hand away from the hot object
- This impulse is relayed across the Synpase to Relay Neurons via synaptic transmission
- Relay Neurons relays impulse to Motor Neurons in the Bicep
- As a result, Bicep will contract to quickly draw hand away from the heat, allowing a rapid response to prevent harm to the body
Cornea
Transparent convex lens that refracts light
Iris
Pigmented membrane that controls the diameter and size of Pupil to alter the quantity of light reaching the Retina
Lens
Transparent disc that changes shape to focus light onto the Retina
Retina
Light-sensitive nerve tissue containing Rods (night vision) and Cones (colour vision) to convert light into electrical impulses to be interpreted by the brain for visual recognition
Optic nerve
Nerve located in the back of the eye that contains Sensory Neurons to send electrical impulses to be interpreted by the brain for visual recognition
Pupil
Opening in the centre of Iris that allows light to enter the Eye
Ciliary muscles
Circular muscle surrounding the lens that that contracts and relaxes to adjust the thickness of lens
Response of eye to distance of near object
- When looking at a near object, incoming light is divergent
- In response, Ciliary Muscles will contract, while Suspensory Ligaments slack
- As a result, the Lens become thicker and more curved, refracting light rays more strongly to meet the Retina
Response of eye to distance of distant object
- When looking at a distant object, incoming light is parallel
- In response, Ciliary Muscles will relax, while Suspensory Ligaments stretch
- As a result, the Lens become thinner and less curved, refracting light rays less strongly to converge on the Retina
Response of eye to changes in light intensity (dark)
- When in dark environment, Photoreceptors - Rods and Cones, detect the change in light intensity
- As a result, reflex occurs involving Muscles in the Iris - Radial Muscles contract and Circular Muscles relax to increase the diameter of the Pupil
- As Diameter of Pupil increases, Pupil dilates to allow more light to enter the Eye to be refracted onto Retina for vision
Response of eye to changes in light intensity (bright)
- When in bright environment, Photoreceptors - Rods and Cones, detect the change in light intensity
- As a result, reflex occurs involving Muscles in the Iris - Radial Muscles relax and Circular Muscles contract to decrease the diameter of the Pupil
- As diameter fo Pupil decreases, Pupil contracts to allow less light to enter the Eye to be refracted onto Retina for vision
Response of Skin to Hot Environment
- When in hot environment, increase in body temperature is detected by Thermoreceptors
- As a result, series of changes occurs in body via thermoregulation
- Blood vessels near skin dilate via Vasodilation to increase blood flow to surface for heat loss
- Sweat glands excrete sweat to cool skin via evaporative cooling
- Hair Erector Muscles relax to lower Skin hair, trapping a thin insulating layer of air above the Skin for heat loss
Response of Skin to Cold Environment
- When in Cold environment, decrease in body temperature is detected by Thermoreceptors
- As a result, series of changes occurs in body via thermoregulation
- Blood vessels near skin contract via Vasoconstriction to reduce blood flow to surface to minimise heat loss
- Sweat glands do not excrete sweat to prevent evaporative cooling
- Hair Erector Muscles contract to raise Skin hair, trapping a thick insulating layer of air above the skin to prevent heat loss
Adrenaline
- Source: Adrenal Gland
- Role: Prepares body for ‘fight or flight’ response
- Effect: Increases heart and breathing rate
Insuline
- Source: Pancreas
- Role: Lowers blood Glucose levels
- Effect: Initiates the conversion of blood Glucose into Glycogen to be stored in Liver and Skeletal muscle
Testosterone
- Source: Testes
- Role: Primary sex hormone in Males
- Effect: Increased levels initiate development of secondary sexual characteristics
Progesterone
- Source: Ovaries
- Role: Primary sex hormone in females to maintain pregnancy
- Effect: Maintains the Uterus lining to cushion fertilised Egg cell
Oestrogen
- Source: Ovaries
- Role: Primary sex hormone in Females
- Effect: Increased levels initiate development of secondary sexual characteristics including the menstrual cycle
