Biology — nervous and endocrine systems (homestasis)

homeostasis

an organisms ability to regulate its internal conditions so reactions can happen at optimal rates

what 3 internal conditions must be regulated?

• blood glucose concentration

• temperature

• water levels

what 2 organs do the central nervous system include?

brain and spinal cord

stimuli

a change in environment

receptor

a specialized cell or protein that detects stimuli

coordinator

processes stimuli information from receptor (brain, spinal cord and pancreas)

effector

muscle, gland or organ which responds to stimuli to restore optimum levels

synapse

the gap inbetween neurons

neurotransmittors

chemicals that are released due to electrical implules and diffuse across the synapse

reflex arc

the pathway which electrical impulses are transmitted quicker for a reflex reaction

reflex action

a rapid and automatic reaction which happens without brain’s conscious part

describe how a reflex action occurs via reflex arc

• stimulus occurs

• receptor cells in the skin detects stimuli

• electrical impulse travels down sensory neurone to relay and motor neurone through the synapse

• chemicals are diffused across the synapse

• effector (glands secrete hormones or muscles contract) will respond

what type of system does this diagram show?
what is it’s function?

central nervous system

sends electrical impulses along neurons

what type of system does this diagram show?
what is it’s function?

endocrine system
releases hormones into blood stream to target cells

which 6 glands are present in the endocrine system?

• pancreas

• ovaries

• testes

• thyroid

• adrenal glands

• piturity (master) gland

hormones

chemicals secreted by glands into the blood

state the function of the pancreas and what hormones are secreted

releases insulin and glucagon to control blood glucose

state the function of the ovaries and what hormones are secreted

which releases female sex hormones, oestrogen and progesterone for menstural cycle

state the function of the testes and what hormones are secreted

releases male sex hormone, testosterone

state the location of the thyroid and what hormones are secreted

in the neck

releases thyroxine which stimulates metabolic rate

state the function of the adrenal glands and what hormones are secreted

releases adrenaline in times of fear or stress

state the location of the pituirity (master) gland and what hormones are secreted

in the brain

secretes several hormones into the blood

explain how the two hormones keep the blood glucose concentration at the correct level in the human body

insulin → glucose too HIGH

• insulin causes glucose to diffuse into liver and muscle cells to be converted into glycogen

• excess glucose converts into glycogen for storage

glucagon → glucose too LOW

• glucagon breaks down glucose in liver cells

• glucose diffuses into blood

negative feedback

process which ensures that changes are reversed and return to optimum levels

Some students investigated the effect of drinking caffeine on reaction time.

Describe how to do the ruler-drop test. [6]

• person 2 measures reaction time of person catching ruler

• person 1 places forearm across a table with their hand open

• person 2 holds ruler vertically, in-between the person 1’s thumb and first finger and drops it randomly

• person 1 must catch the ruler as soon as it is dropped

• person 2 records measurement just above person 1’s thumb

• repeat test to calculate mean

state the variables for the ruler drop experiment

• IV: person drinks coffee

• DV: reaction time

• CV: starting distance of ruler