The Nervous System Health Science Technology

Journal: Fun Brain Facts How much does a human brain weigh? How about an elephant or rat brain? How much energy does your brain generate when you “think”? What percentage of the brain is water? What percentage of your body’s oxygen intake does the brain use? Can the brain feel pain?

Answers The human brain weighs about 3lbs. An elephant’s 15lbs and a rat 0.04lbs. Generates about 10 watts of energy – like a small night light bulb – so that “idea” bulb over your head is not a bad illustration! 80% of brain is water and though it only makes up about 2% of the body’s mass, it uses 20% of the oxygen supply. It is very sensitive to lack of oxygen – so breathe deeply and keep it happy (: No pain in the brain - you can be awake during brain surgery once the cutting past scalp and cranium and linings is done!

The Nervous System is composed of the central and peripheral systems. Central is brain and spinal cord Peripheral is composed of nerves including cranial and spinal. Also includes Autonomic Nervous System

Function of Nervous System Sensory function – gathers information from inside & outside the body to send to the CNS Integrative function – takes nerve impulses (information) received to CNS and integrates them to create sensation, add to memory, and produce thought, and decisions are made and acted on by motor function. Motor function – carry nerve impulses from CNS to effectors (muscles, glands) for action!

Neuron Basic functional unit functional unit of nervous of nervous system. system.

Components of Neuron Cell body – has all basic structure of cells including nucleus but mature neurons do not seem to reproduce. Has Nissl bodies that function as rough endoplasmic reticulum. Dendrites – neurofibril extensions of cell body that receive and carry impulses to cell body. Cell may have many dendrites. Axon- neurofibril extension of cell body that carries impulses away from cell body. Neuron only has one axon.

Components of Neuron Schwann cells – create the myelin sheath (lipoprotein cover) around axons of peripheral nerves. Insulates and speeds transmission of nerve impulses. These are not nerve cells but neuroglial cells that are support and structure for the nervous system.

How Neurons Communicate Synapse- space between neurons or between neurons or receiving receiving structure structure Neurotransmitter- chemical chemical substance substance secreted to carry secreted to carry impulse across impulse across synapse synapse

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Reflex Arc The knee jerk reaction or patellar reflex is an example of the most simple response involving one each sensory & motor neurons & spinal cord –nerve pathway

Quiz What it the basic cell unit of the nervous system? What is the function of dendrites and axons? What is the purpose of myelin sheath on an axon? What is the space between neurons? What communicates messages between neurons across this space? Word Bank on White Board

Coverings of CNS Besides the protection of cranial cavity and vertebral cavity – the CNS is covered by three layers of protective membranes called the meninges. Dura mater – tough outer layer over brain, spinal cord Dura mater – tough outer layer over brain, spinal cord Epidural Space – between dura & vertebrae for cushion Arachnoid mater – middle layer Arachnoid mater – middle layer Subarachnoid space – filled with Cerebrospinal fluid (CSF) around brain & spinal cord to protect Pia mater – thin inner layer w/ nerves & blood vessels, where CSF is made Pia mater – thin inner layer w/ nerves & blood vessels, where CSF is made

CSF & Ventricles CSF –surround brain & spinal cord in the the sub-arachnoid space, allows the structures to “float” protecting from jarring injury, maintains ion balance and provides transport to the blood for waste products. Ventricles are a series of interconnected cavities in the brain filled with CSF

Ventricles

CSF – Lumbar Puncture A procedure called a Lumbar Puncture can be done to measure pressure of the CSF and obtain a sample

Brain Parts Brain stem – Medulla Oblongata – lowest part brain stem. Connects with spinal cord. Regulates heart rate, respiration, swallowing, coughing, and blood pressure Medulla Oblongata – lowest part brain stem. Connects with spinal cord. Regulates heart rate, respiration, swallowing, coughing, and blood pressure Pons – Conducts messages to other parts of the brain and reflex actions including chewing, tasting, saliva production, some respiration Pons – Conducts messages to other parts of the brain and reflex actions including chewing, tasting, saliva production, some respiration Midbrain- top of brain stem. Conducts impulses and eye and auditory reflexes. Midbrain- top of brain stem. Conducts impulses and eye and auditory reflexes.

Brain Parts Diencephalon- located between brain stem and cerebrum. Contains: Thalmus – relay center for sensory impulses to cerebrum Thalmus – relay center for sensory impulses to cerebrum Hypothalmus – involved in emotions such as rage, fear and pleasure; regulates and controls autonomic nervous system, temperature, appetite, water balance, sleep, blood vessel constriction and dilation - many through pituitary gland releases. Hypothalmus – involved in emotions such as rage, fear and pleasure; regulates and controls autonomic nervous system, temperature, appetite, water balance, sleep, blood vessel constriction and dilation - many through pituitary gland releases.

Autonomic Nervous System Involuntary – regulates activities of internal organs Sympathetic regulates "fight" or take "flight" (run away) Parasympathetic allows us to "rest" and "digest.“ (slow us down) The ANS regulates: Muscles -- in the skin (around hair follicles - smooth muscle) -- around blood vessels (smooth muscle) -- in the eye (the iris; smooth muscle) -- in the stomach, intestines and bladder (smooth muscle) -- of the heart (cardiac muscle) -- in the skin (around hair follicles - smooth muscle) -- around blood vessels (smooth muscle) -- in the eye (the iris; smooth muscle) -- in the stomach, intestines and bladder (smooth muscle) -- of the heart (cardiac muscle) Glands – such as adrenal glands that release epinephrine

Brain Parts Cerebellum – muscle coordination and tone; balance and posture Corpus Callosum – connects and transmits impulses between hemispheres of brain.

Brain Parts Cerebrum – largest and highest section. Outer layer arranged in folds called convolutions. Separated into two hemispheres – right and left. Each has 4 lobes named for bones: frontal, parietal, temporal and occipital

Brain Parts Frontal lobe: emotions, personality, morality, intellect, motor speech (Broca’s area), ipsilateral motor control Parietal lobe: sensory, motor, pain, heat, touch Temporal lobe: hearing auditory comprehension (Wernike’s area), memory, smell Occipital lobe: vision and visual perception

Q&A Does your brain or spinal cord regenerate neurons that are damaged? No, but work is being done with stem cells in hopes of using them as repair material. No, but work is being done with stem cells in hopes of using them as repair material. At what level of spinal cord injury will you be a quadriplegic? A paraplegic?

Q&A What is an infection of the linings of your brain called? Meningitis Meningitis What is the correct term for “brain surgery”? Craniotomy Craniotomy