Living in the environment: regulation and control

Processes Heat Generation Heat Input Heat Output

Homeostasis: the maintenance of relatively stable conditions in the internal environment of the body despite variations in the external environment. Factors such as: – blood pressure, – body temperature, – respiration rate, – blood glucose levels – pH – Ions – O 2 and CO 2 levels – Nutritional needs – H 2 O levels are maintained within a range of normal values around a set point despite constantly changing external conditions.

Homeostasis requires the body being able to : – detect external changes – Implement internal changes to compensate

The Stimulus - Response Model

Heat Cools

The Stimulus Response Model How can the body control the response? 1.Disrupt the signal transduction pathway 2.Removal of the original stimulus 3.Responding in a way that alters the original signal. Feedback

Negative feedback mechanisms

Negative Feedback

Negative Feedback Mechanism

Positive feedback Works by adding to the stimulus and increasing the effect of it.

Positive feedback

Mechanisms enabling Homeostasis Negative feedback model

Modes of Transmission Hormonal system Slow ( cm/sec) Act by binding to specific receptors on target cells after travelling through the blood stream. Can be more long term effect Nervous system Fast ( 1-120m/sec) Act by sending electrical impulses along neuron cells. Short term effect.

The nervous system is a rapid response to stimuli. It is a more direct communication pathway than hormones.

There are 2 main parts to the Nervous System: – The peripheral nervous system – The central nervous system

Nerve Structure

The nervous system is made up of neuron cells that send an electrical impulse along from one neuron to the next. Action Potentials

Basic types of neurons

receptor effector

The Nerve impulse Nerve impulse s are an electrical signal that travels along an axon. There is an electrical difference between the inside of the axon and its surroundings,. When the nerve is activated, there is a sudden change in the voltage across the wall of the axon, caused by the movement of ions in and out of the neuron. This triggers a wave of electrical activity that passes from the cell body along the length of the axon to the synapse.

The synapse The Synapse There are hundreds of different types of neurotransmitters, each of which control something different. This makes the nervous system controllable, meaning some neurotransmitter initiate a response while others block a response. Neurotransmitters

Receptors in the Skin

Types of sensory receptors

CNS

Many responses are a reflex; not under conscious control.

Explain somatic nerves, autonomic nerves, parasympathetic and sympathetic.

Hormones Hormones are signalling molecules or chemical messengers that control many functions in the bodies of organisms. eg t emperature, blood glucose levels, calcium uptake and many many more are controlled by hormones.

Hormones at work. Scary

Cells that produce hormones and are clustered into organs.

When the homeostatic control of Blood sugar is disrupted: Diabetes Type 1 Diabetes Type 2 Diabetes

Cushing's disease-Pituitary Gland The pituitary gland secretes hormones regulating homeostasis, including tropic hormones that stimulate other endocrine glands. It is functionally connected to the hypothalamus by the median eminence via a small tube called the Pituitary Stalk. It is considered to be the "master gland".

Thermoregulation animation countercurrent heat exchange

A ind of dormancy shown by insects, where they pause a part of their lifecycle. (Flies in winter??) When food is scare and the temperature is low. Some animals can’t maintain a stable internal temperature. So instead they hibernate! (Below: Dormice)

Ways that water can be lost Panting in dogs, dingos & wolves Sweating Urine Faeces

Ways to save or increase water supply Thirst response- experienced as the concentration of water in the blood is lowered Waterproof barriers like; hair, feathers, scales and skin protect against evaporative water loss. Reabsorption of water from the large intestine. Increase in concentration of urine by increasing reabsorption of water in Kidneys. Storage of water. – (Desert frogs store water in a cocoon, – Camel’s store fat in their hump and metabolise the fat to gain water

Saltwater Marine saltwater animals tend to have body fluids that are HYPOTONIC to their surroundings. So they lose water via osmosis to their surroundings. To gain more water they drink salt water and must spend a lot of energy removing salt from their body. Freshwater Freshwater animals have lots of water in their surroundings but have body fluids that are HYPERTONIC to their surroundings. So they can gain too much water from their surroundings, causing their cells to burst.

External : Hi H 2 O LO SaltsExternal : LO H 2 O Hi Salts Internal : Hi H 2 O LO SaltsInternal : LO H 2 O Hi Salts