Communication

What are features of a good communication system

• cells must be able to signal with each other

• flexibility - diff types of responses

• rapid

• wide ranging - responses cover whole of body

• specific - target cells

What are the key features of the nervous system

• sends messages via electrical impulses within neuron

• rapid action

• short-term responses

• precise areas of response

What are the key features of the endocrine system

• chemical protein messengers travel through bloodstream

• slower action

• long-term responses

• widespread areas of response

Define homeostasis and examples

• maintenance of a stable internal environment despite changes in external environment

• temp, pH, BG levels, water levels, waste-urea,CO2

Define negative feedback and example

• mechanism that counteracts a change, returning a condition to the normal

• thermoregulation

Define positive feedback and example

• mechanism that amplifies a change, increasing from the normal until a specific outcome

• oxytocin during contractions

What is an endotherm

• organism that can use internal sources of heat to maintain its body temperature

What are advantages of being an endotherm

• inhabit colder regions

• activity possible when external temp is low

• fairly stable temperature (irrespective of external)

What are disadvantages of being an endotherm

• significant amount of energy required to thermoregulate

• less energy available for growth

• higher food intake required

What is an ectotherm

• organism that relies on external sources of heat to regulate its body temperature

What is an example of an ectotherm and how does it thermoregulate

• reptiles use solely behavioural categories to regulate

• to heat up: bask in sun, low metabolic activity

• to cool down: seek shade, eat, high metabolic activity

What are advantages of being an ectotherm

• use less energy from food

• can survive longer periods without food

• use a greater proportion of energy for growth

What are disadvantages of being an ectotherm

• less active in cooler environments

• dont inhabit colder regions

• may not be capable of activity in winter/night

• risk of predation

What is thermoregulation

• body maintains stable internal temp (37°)

• controlled by hypothalamus - with thermoreceptors to detect changes

How is temperature maintained when there is a cooler environment

• thermoreceptors in thermoregulatory centre in hypothalamus detects fall in temp

• vasoconstriction: narrowing of arterioles further away from skin surface, so less heat lost through radiation

• shivering: muscle contraction increases metabolic rate so more heat gain

• less sweating: less cooling by evaporation

• hairs on skin stand: creates an insulating layer to trap heat

How is temperature maintained when there is a hotter environment

• thermoreceptors in thermoregulatory centre in hypothalamus detects raise in temp

• vasodilation: dilation of arterioles closer to skin surface, so more heat lost through radiation

• sweating: cooling by evaporation

• less shivering

• hairs on skin lay flat: no air trapped as heat

What is a sensory receptor and its role

• specialised cells that detect environmental stimuli

• act as energy transducers - convert one type of energy into an electrical impluse -

What is an example of a sensory receptor and its specific role

• pacinian corpuscle

• detects vibrations and pressure changes

• converts pressure changes into electrical impulses

Where can pacinian corpuscles be found

• skin - fingers, soles

• joints

• muscles

• tendons

How does the pacinican corpuscle work to initiate a response

• stimulus (change in pressure detected)

• lamellae surrounding the neuron ending becomes deformed

• causes stretch-mediated Na+ channels to open

• influx of Na+ ions, creating a generator potential

• if this potential meets the threshold, an action potential is triggered

What is the structure and function of a sensory neuron

• detects stimuli and carries electrical impulses from sensory receptors to the CNS

• long axon

• cell body containing nucleus, mitochondria, ribosomes

• dendrites connecting to other neurons

• dendron

• myelin sheath

• nodes of ranvier

What is the structure and function of a motor neuron

• carries electrical impulses from CNS to effectors

• longer axon

• cell body containing nucleus, mitochondria, ribosomes

• dendrites connecting to other neurons

• myelin sheath

• nodes of ranvier

What are the similarities between neurons

• dendrites connecting to other neurons

• long axons that carry electrical impulses

• myelinated

• nodes of ranvier

• cell body with nucleus

What are the differences between sensory and motor neurons

• sensory: cell body at middle not in CNS, motor: cell body at end of axon in CNS

• sensory: dendrites on axon, motor: dendrites attached directly on cell body

• sensory: shorter axon, motor: longer axon

• sensory: dendron present, motor: dendron absent

• sensory: starts at sensory receptor, motor: ends at motor end plate

What is the function of relay neuron

• carry impulses from the sensory to motor neuron

• only in CNS