B10 - The human nervous system

Homeostasis is the regulation of the interanl condiations of the cell or organism to maintain optimum (the best) conditions for function, in response of internal and external changes. (Keeping interanl body conditions constant).

Things that need to be CONSTANT:

• Urea
• Carbon dioxide
• Water
• Temperataure
• Blood glucose levels

• Produced in the LIVER from protein and AMINO ACIDS (Amino acids get broken down when we eat too much (excess) protein and when cells/tissues break down)

• Needs to be removed because it is TOXIC and can damage cells

Flow chart of the removal

Amino group coverted into urea > Travel through blood vessel to kidney > Filtered by kidney > Stored in bladder > Passed out the body through urine

• Produced by RESPIRATION (waste product).

• Needs to be removed because it creates an acidic solution when dissolved - low pH in cells affects how well enzymes work and can possibly denature them.

Flow chart of removal

Respiring cells > Blood > Lungs > Exhaled into the air

• Produced by RESPIRATION (waste product), DIET.
• Needed for metabolic reaction so is taken in via diet.

• Needs to be removed because too much water movement damages cells by osmosis.

• Lost through: Urine, Sweat and Exhalation

• Consumed in DIET
• Important for respiration
• If blood sugar is too high, the pancreas releases insulin which coverts glucose into glycogen and is then removed from the blood
• Too much glucose can cause diabetes if the pancreas doesn't produce enough insulin
• Diabetes can be treated by eating carefully or Iinjecting extra insulin

• Poduced by ACTIVITY and ENVIRONMENT
• Temp enzymes work best at
• Normal internal body temp = 37℃
• Needs to be removed because enzymes denature above 40℃ and slow down when cold
• Controlled by sweat, vasodilation, shivering, goosebumps

Cells that detect change sin the environment

(ear, nose, eye, skin)

Changes in the environment 

(an object eg. a cat)

Muscles or glands that bring about a response 

(Salivary glands, skeletal muscle, pancreas)

Areas that recieve and process information. They coordinate a response

(Brain & Spinal cord)

• Uses electrical impulses to allow you to react quickly to the environnment and coordinate what you do
• Made up of neurones
• Neurones send messages as tiny electrical impulses - these are very fast so we can react to changes very quickly

• IMPULSES NOT MESSAGES
• Neuorne - 1 nerve cell
• Nerves - a bundle of neurones

Stimulus> Receptor > Sensory nerve > CNS (central nervous system) > Montor neurone > Effector

Sensory neurone - sends electrical impulses TO the CNS/coordination centre

Motor neurone - sends electrical impulses to the effector 

Ears - sound, position (balance)

Eyes - light

Skin - touch, pressure, pain, temperature

Nose & tongue - smell, taste

• Distractions 
• Tiredness
• Gender
• Medical conditions 
• Age 

Drugs

• Alcohol - depressant (increases reaction time)
• Caffiene - stimulant (decreases reaction time)

Variables

IV (changes) -  With and without caffiene

DV (outcome) - Reaction time, distance the ruler is caught

CV (stays the same) - Position of the hand, the student, height and force the ruler is dropped

Risks - spillages mopped up to avoid slipping, no drinking in the lab, sharp objects of ruler

'Hypothesis'

The students reaction time will decrease after they drink the cola which will make their reaction to catching the ruler quicker.

This will happen because cola contains caffiene which is a stimulant.

Reflexs actions BYPASS the brain (no thinking time) to avoid damage/harm to the body - faster reaction time

Examples of reflex actions:

• Knee jerks
• Sneeze
• Flinching
• Touching hot/sharp objects

Reflex pathway

Stimulus (a hot object) > Receptor (skin)  > Sensory neurone > RELAY neurone > Motor neurone > Effector (arm muscles contract)

A synapse is the space between two neurones. Here, chemicals diffuse from one neurone to the next, allowing the message to continue