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B10 The Human Nervous System (Human nervous system (Required Practical (IV…
B10 The Human Nervous System
Homeostasis
regulating and maintaining a constant internal environment
in response to internal or external changes
for optimum cell functions and enzyme action
water content
leaves body by breathing
sweating also removes salt
excess water removed in urine
body temperature
constant core temperature for enzyme activity
exercising heats up muscles
blood glucose concentration
eating increases glucose in blood
relies on automatic
controls systems
nervous control system
nervous responses
short effect
fast reacting
hormonal control system
chemical responses
long term effect
slow acting
KEY features
Receptors
detect
stimulus
changes external or internal environment
Coordination centres
receive and process information from receptors
sends signals to coordinate response
Effectors
gives
response
to stimuli
restores optimum body conditions
Human nervous system
Receptor cells
in
sense organs
nose
tongue
ear
skin
eye
neurones (nerve cells)
in nerves
pass electrical impulses along
Sensory neurone
from receptors to CNS
Motor neurone
from CNS to effectors
Central Nervous System (CNS)
brain
&
spinal cord
processes information from sensory receptors
sends out impulses along motor neurone
Effector
mucles
contract
glands
secrete chemicals
Required Practical
Measuring reaction times
Method 2:
'' Ruler drop test ''
person A sits and places dominant forearm over the desk with hand overhanging
person B holds a meter ruler vertically so that the 0cm is between person A's thumb and first finger
Person B drops the ruler at a random time and person A reacts to catch it as quickly as possible
take and record the measurement on the ruler that is above person A's thumb
repeat test several times and calculate a mean, then use a conversion table to convert results to a reaction time
repeat experiment for person B or/ investigate factors affecting human reaction times (e.g. caffeine, distraction)
IV (*only one)
affecting factors
caffeine - drink cola
also use caffeine free cola for control
other chemicals in cola
measured volume
drink 30 min before test
different person
different hand
amount of practice
DV
measured reaction time
CV
always measure ruler at top of thumb
constant starting distance between thumb and first finger
same room conditions (e.g. lighting and background noise)
Safety: don't eat or drink in the lab/ ensure cola caffeine drink is safe, no medical conditions e.g. allergy or heart condition
Method 1
: use digital sensors to measure how quickly you react to a visual stimulus
Reflex Actions
rapid automatic response
does not involve conscious parts of brain
fast to avoid danger
basic body movements without thinking
breathing
moving food along digestive system
Reflex Arc
(pathway)
receptor
detects
stimulus
sensory neurone
transmits electrical impulse to CNS
relay neurone
in CNS passes on impulse
motor neurone
transmits impulse to
effector
effector is stimulated to give a
response
relay neurone is the coordinator
in the spinal cord or in unconscious parts of the brain
Synapse
a gap at junction between 2 neurones
electrical impulse arrives at synapse
chemicals released from sacs
chemicals diffuse between gap to transmit impulse
chemical attach to receptor site on of next neurone
neurone sets up a new electrical impulse
chemical diffusion is slower than electrical impulse
an impulse also sent to conscious areas of brain
you know about the reflex action after it has happend
