11.1 The Nervous System.
1 .The nervous system of a mammal consists:
- The central nervous system (CNS) comprising the brain and the spinal cord.
- Te peripheral nervous system (PNS) comprising the cranial nerves, spinal nerves and sense organs.
2 . A neurone is a nerve cell. A nerve fibre is a long protoplasmic extensions of the cell body of a neurone. It serves to transmit impulses.
3 . A nerve is a collection of nerve fibres.
4 . Neurones:Sensory
1 ) Sensory neurones:
- It is a receptor neurone,
- It transmits impulses from the sense organ (receptor) to the CNS.
2 ) Motor neurone:
- It is an effector neurone.
- It transmits impulses from the CNS to the effectors.
3 ) Relay neurone:
- It connects sensory neurones to motor neurones.
5 . A synapse is a junction between two neurones. A dendron transmits impulses towards the cell body of a neurone. An axon transmits impulses away from the cell body of a neurone.
6 . Structure and functions of the human brain:
7 . Reflex actions involve messages being transmitted from the sensory neurone to the motor neurone without involving the conscious part of the brain.
8 . A reflex arc is the shortest pathway by which impulses travel from the receptor to the effector in a reflex action.
11.2 The Eye.
1 . Structure and functions of the eye:
Fig.11.2 Structure of the eye.
2 . Accommodation is the ability to change the curvature of the lens, so that light rays continue to be focused on the retina.
1 . Hormones are chemical substances produced by a gland, carried by the blood, to the target organ(s), and produce a response, and destroyed in the liver.
2 . Since hormones are proteins, therefore they are affected by pH and temperature.
3 . The pituitary gland plays an important role as a “controller”. It secretes a number of hormones, each of which controls the activity of a particular gland, hence the pituitary gland is sometimes referred to as the “master gland”.
4 . Location of endocrine gland:
5 . The islets of Langerhans are the special group of cells in the pancreas which secrete the hormone insulin into the bloodstream.
6 . Adrenaline:
7 . Insulin:
11.4 Diabetes Mellitus.
1 . Signs of diabetes mellitus:
- A persistently high blood glucose level and glucose in the urine after a meal are signs of diabetes mellitus.
2 . Treatment:
3 . An insulin-dependent person is a person who needs daily injections of insulin.
4 . An insulin-independent person is a person who doesn’t usually require any injections of insulin.
Type 1 diabetes (Juvenile-onset diabetes=early-onset diabetes=insulindependent diabetes)
Type 2 diabetes (Adult-onset diabetes=late-onset diabetes=insulin-dependent diabetes)