Biology Hacked: Summary of Human Nervous System and Nerve Cells

Summary: Human Nervous System

In high-school and looking for a quick revision resource? Here are some summarized notes from my year 9 biology test. It includes the CNS, PNS, autonomic nervous system, somatic NS, different receptors, the structure of nerve cells. 

Nervous Systems

Central Nervous system (CNS)

·        Brain

·        Spinal Cord

Peripheral Nervous System (PNS)

·        Cranial Nerves

·        Spinal Nerves

Split into two parts

·       1. Somatic NS

·        Collects information from sensory organs and coordinates movement of the body

·        Receptors -organs or tissues that can detect changes in the environment (stimulus)

o   Photoreceptors-The sense of sight

§  Messages sent to optic nerve=vision

§  Two types=cones(colour vision) and rods(dim light, night vision)

o   Chemoreceptors-tasting food

o   Mechanoreceptors-touch and muscles being stretched (feeling full)

o   Thermoreceptors-changes in temperature

o   The ear

§  Receptors grouped together and helps hearing and balance. (Semicircular canals cause fluid to move causing a nerve impulse to be sent).

o   Receptors found in the skin include: pressure, pain, temperature

·        2. Autonomic NS

·        Consists of two parts,

o   Sympathetic-speeds up the functions of the body making it work my efficiently. Emergencies.

o   Parasympathetic-slows things down. Resting.

o        Effects	o        Sympathetic	o        Parasympathetic
o        Blood flow	o        Decrease in digestive system o        Increase to heart and lungs	o        Increase in digestion
o        Digestion	o        Stops peristalsis	o        Increases peristalsis o        Increase saliva
o        Airways	o        Open bronchioles	o        Reduces diameter of bronchioles
o        Heart rate	o        increases	o        decreases
o        Eyes	o        Pupils dilate	o        Close vision

Nerve Cells

Neurones/nerve cells

·        Axon-A single nerve fibre which carries nerve impulses away from the cell body

·        Dendrites- Branch out from the cell body and carry impulses to the cell body. This allows them to be in contact with multiple nerve cells.

·        Cell body- Contains nucleus and cytoplasm. The control centre of the cell

·        Synaptic knobs-Pass messages to the next neurone

·        Synapse-the gap between two neurones where neurotransmitters are released carrying the message

·        Myelin sheath- Fatty materials that insulate the axon and increase the speed of nerve impulses.

o   Nerve cells covered in myelin sheath are known as white matter.

o   The outer part of the brain is made out of grey matter.

Nerve impulses

·       electrical messages

·        travel in one direction only- from the axon of one cell to the dendrite of another