1. The Human Nervous System and The Human Endocrine System Dr. Rose

2. Divisions of the Nervous System
The human nervous system is divided into central and peripheral components.
1. Central Nervous System (CNS) consists of the brain and the spinal cord.
2. Peripheral Nervous System (PNS) consists of nerves outside the CNS.

4. The Neuron
The cells that carry messages throughout the nervous system are called neurons.
Whatever their specific function, all neurons have the same physical parts: The cell body, dendrites and the axon.

6. Neuron Structure A neuron consists of 3 main parts:
Cell Body - contains the nucleus
Dendrites - short branch extensions spreading out from the cell body. These receive the impulse.
Axon – a long fibre that carries impulses away from the cell body. The axons of most neurons are covered with a lipid layer known as the myelin sheath which acts as an insulating material.

9. Neuron Types Neurons can be classified into 3 main types:
1. Sensory neurons carry impulses from the sense organs/receptors to the CNS.
2. Relay (Inter) neurons carry impulses from neuron to neuron within the CNS.
3. Motor neurons carry impulses from CNS to muscles and glands/effectors.

10. Reflex Arcs
Neurons are linked in functional pathways called reflex arcs.
A reflex action is an automatic response which you cannot control.
Reflex arcs can be illustrated by using the Stimulus-Response Model.

12. Stimulus-Response Model
Something in the environment which causes a behaviour response is a stimulus.
The receptor (sense organ) detects the stimulus, a message is sent to the effector (muscle/gland which responds to nerve impulse) which brings about a response.
The entire nervous system provides a system of interconnecting links between receptors and effectors.

14. The Synapse
Neurons that transmit impulses to other neurons do not touch one another. The small gap between the axon of one neuron and the dendrites on the next neuron is called the synapse.
The synapse ensures one-way transmission of impulses. A nerve impulse cannot go backwards across a synapse.

16. Transmission of Nerve Impulses
Messages move down the axon as electrical impulses
The movement of sodium (Na+) and potassium (K+) causes the impulse
Once it gets to the synapse it stops
Chemical messengers called Neurotransmitters then pass the message through the gap to the dendrites of the next neuron

20. The Human Brain The human brain consists of two types of tissue:
White matter is tissue made of axons.
Grey matter is tissue made of cell bodies.
There are 3 main divisions to the human brain:
The Cerebrum, Cerebellum and Brainstem

24. The Cerebellum Coordinates movement.
Responsible for balance and performing some cognitive abilities such as those involved in speech and language.
Also involved in hand – eye co-ordination

25. The Brainstem The most primitive part of the brain
Controls vital, reflexive functions such as breathing, blood pressure
Also swallowing, vomiting and digestion

26. Diencephalon
Thalamus: Link between the cerebrum and the rest of the brain
Hypothalamus and Pituitary: Makes hormones and links the nervous system to the endocrine system

27. The Cerebrum Made up of two parts- left and right hemispheres.
Responsible for cognitive processes such as learning, memory and thinking.
Can be divided into 4 lobes:
Frontal- thought,speech, movement, motivation, foresight, emotions and feelings
Parietal- touch, taste, some speech
Occipital- sight, visual recognition
Temporal- auditory and smell

28. Nervous control
Hormonal control
Communication
Impulses across synapses
Hormones in the blood
Speed
Very rapid (ms)
Relatively slow (min – hour or longer)
Duration
Short term & reversible
Longer lasting
Target pathways
Specific (through nerves) to specific cells
Hormones broadcast to target cells everywhere
Action
Causes glands to secrete or muscles to contract
Causes changes in metabolic activity

29. The Human Endocrine System
The endocrine system consists of glands
which release hormones.
Endocrine glands are ductless- they don’t release their product into a duct as exocrine glands (salivary, sweat) do.
Instead endocrine glands secrete hormones into the blood which transports them around the body.

30. The Human Endocrine System
As the hormones pass cells, only those with special receptors will react to the presence of the hormone. These are called target cells.

32. Pituitary gland

33. Pituitary gland
Known as the master gland because it secretes a number of hormones which influence other endocrine organs.
Makes human growth hormone.

34. Thyroid gland

35. Thyroid gland
Secretes thyroxine which controls metabolic rate and is important in regulation of body temperature.
Iodine is important for the thyroid tissue.
Goiter results from lack of iodine.

37. Adrenal glands

38. Adrenal glands
Secrete adrenaline which is called the fight or flight hormone because it prepares the body for action.
More glycogen is converted to glucose
Faster heartbeat
The above all help to provide more glucose and more oxygen for working muscles.

39. Pancreas

40. Pancreas Regulates sugar balance
Secretes two hormones: insulin and glucagon
Insulin lowers blood sugar and stores it as glycogen.
Glucagon increases blood sugar by stimulating glycogen breakdown.

41. Negative Feedback
Blood glucose concentration is regulated by negative feedback.
High blood sugar
Low blood sugar
Pancreas makes
insulin
Pancreas makes glucagon
Sugar enters cells
Glucose to glycogen
Sugar leaves liver
Glycogen to glucose
Blood sugar level lowered
Blood sugar is increased

42. Diabetes
Diabetes is a condition where there are higher than normal blood glucose levels.
Usually the result of the failure of the pancreas to secrete enough insulin.
Treatment is by regular injection of pure insulin- much of this is now manufactured by genetic engineering.