cns (central nervous system)

MAJOR DIVISIONS OF THE NERVOUS SYSTEM

FUNCTION

Functions of the Nervous System Control and communication system Monitors Changes inside and outside thebody (sensory input) Processes and interprets sensory input andmakes decisions (integration) Affects a response (motor output) by

affectingglands, muscles etc. Works closely in conjunction with the

endocrine system

NEURONS

Nerve Transmission

Neurons - Basic anatomic and functional unit of the nervous system

Respond to sensory and chemical stimuli, conduct impulses and release specific chemical

regulators A nerve impulse is a wave of electrical charge

sweeping from neuron to neuron The gap lying between one neuron and the next is the

synapse Neurotransmitters move across the synapse

where they excite, inhibit or modify

MENINGES

3 layers that lay directly on the surface of the brain tissue (parenchyma) and spinal cord. Offer a cushioning effect.

• Dura Mater - outer most layer that is thick and fibrous, that lines

the interior of the skull.

• Arachnoid - middle layer, is extremely thin and loosely encloses

the brain

• Pia Mater - inner most, mesh like and very vascular. It follows the convolutions of the brain

Meninges

• Spaces of the meninges - extradural, subdural and subarachnoid

VENTRICULAR SYSTEM

Produces (~ 500mL/day) and circulates (~ 150mL) CSF.

• CSF is usually a clear colourless fluid that acts as a shock absorber

• The ventricular system is connected to the subarachnoid space (SAS)

• 3 main compartments - 2 lateral ventricles, 1 third ventricle and

1 fourth ventricle

• CSF is produced by the choroid plexus in each ventricle

• CSF is reabsorbed into the venous blood flow via the arachnoid villi

• Arachnoid villi are small granulations that project from the SAS into the venous outlets of the brain.

What are the major parts of the nervous system?

The major divisions of the nervous system include:

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)

3. Autonomic Nervous System (ANS)

a. sympathetic nervous system

b. parasympathetic nervous system


1. Central Nervous System consists of the brain and

the spinal cord functions as a

switchboard that controls and coordinates the activities of the whole nervous system


2. Peripheral Nervous System

carries all the messages sent between the central nervous system and the rest of the body


3. Autonomic nervous system

controls involuntary activity such as the action of the heart and glands, breathing, digestive processes, and reflex actions



a. sympathetic system responds to the

body’s needs during increased activity and in emergencies.

controls heartbeat, blood circulation, respiration and other unconscious activities.



b.parasympathetic system

opposes the actions of the sympathetic system.

slows down heartbeat, diverts blood circulation, etc.

PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS

1. Brain organ of thought and feeling responsible for issuing nerve

impulses, processing data, and the master control center over the body

divided into cerebrum, cerebellum and the brainstem


1. Brain

a. Cerebrum forms the bulk of the

brain responsible for the

higher thought processes such as memory, judgment and reason


1. Brain

a.1Parts of the Cerebrum Frontal lobe planning,

consciousness, speech, memory, and reasoning


1. Braina.1Parts of the Cerebrum Parietal lobe houses the control

centers for processing impulses related to the sense of touch; temperature, texture, size, shape and weight


1. Brain

a.1Parts of the Cerebrum Occipital lobe contains the centers

responsible for sight.


1. Brain

a.1Parts of the Cerebrum Temporal lobe houses centers for the

processing and correlation of the auditory (hearing) and olfactory (smell) senses.


1. Brain

b. Cerebellum responsible for body

balance, posture and the coordination of movement

receives, coordinates and modifies orders from the cerebrum


1. Brain

c. Brain stem connects the

cerebrum with the spinal cord

consists of the midbrain, pons, and medulla oblongata


1. Brain

c. Brain stem pons – located

between the midbrain and the medulla oblangata; connects the cerebellum and the cerebrum


1. Brain

c. Brain stem medulla oblangata –

lowest part of the brain stem; controls involuntary processes such as the heartbeat, breathing, digestion and body temperature regulation.


1. Brain

c. Brain stem Mid brain – the middle

part of the three main divisions of the brain; helps control the movement of the eyes and the size of the pupils


2. Spinal cord allows signals to be sent from the

brain to the parts of the body receives messages from the parts

of the body to the brain acts as a coordinating center

responsible for some simple reflexes

CRANIAL NERVES

BLOOD SUPPLY

BRAIN BLOOD SUPPLY

INTERNAL CAROTID ARTERY • Not all ICA occlusions become symptomatic.

It depends on the amount of collateral blood supply primarily

from the C of W • The degree of deficits vary, from

asymptomatic to a catastrophic infarction (similar to MCA

MIDDLE CEREBRAL ARTERY • MCA is the largest branch that comes off the

ICA • It has deep branches that supply part of the

internal capsule and basal ganglia (putamen, caudate nucleus and

globus pallidus) • It passes out to the lateral surface of the

cerebral hemisphere where it supplies blood to the cortical areas of the

temporal, frontal and parietal lobes

The Endocrine System

Controls many body functions exerts control by releasing

special chemical substances into the blood called hormones

Hormones affect other endocrine glands or body systems

Derives its name from the fact that various glands release hormones directly into the blood, which in turn transports the hormones to target tissues via ducts.


Exocrine glands - transport their hormones to target tissues via ducts.

Endocrine Emergencies: from common:

Diabetes to the unusual:

Thyrotoxicosis


Consists of several glands located in various parts of the body.

Pituitary gland: a small gland located on a stalk hanging from the base of the brain - AKA

“The Master Gland” Primary function is to

control other glands. Produces many

hormones. Secretion is controlled by

the hypothalamus in the base of the brain.


The Pituitary Gland is divided into 2 areas, which differ structurally and

functionally each area has

separate types of hormone production.

The two segments are: Posterior Pituitary:

produces oxytocin and antidiuretic hormone (ADH)

Anterior Pituitary: produces thyroid-

stimulating hormone (TSH)

growth hormone (GH) adrenocorticotropin

(ACTH) follicle-stimulating

hormone (FSH)


And even more… luteinizing hormone

(LH) prolactin

Let’s go over these one at a time...

Posterior Pituitary Oxytocin (the

natural form of pitocin) stimulates gravid

uterus causes “let down” of

milk from the breast. ADH (vasopressin)

causes the kidney to retain water.


Anterior Pituitary Primarily regulates

other endocrine glands

rarely a factor in endocrinological emergencies

TSH stimulates the thyroid gland to release its hormones, thus metabolic rate

Anterior Pituitary… Growth hormone (GH)

glucose usage consumption of fats

as an energy source ACTH stimulates the

adrenal cortex to release its hormones

FSH & LH stimulates maturation & release of eggs from ovary.


The Thyroid Gland lies in the anterior

neck just below the larynyx.

Two lobes, located on either side of the trachea, connected by a narrow band of tissue called the isthmus.

Sacs inside the gland contain colloid

Within the colloid are the thyroid hormones: thyroxine (T4) triiodothyronine (T3)

When stimulated (by TSH or by cold), these are released into the circulatory system and the metabolic rate.

“C” cells within the thyroid produce the hormone calcitonin.


Calcitonin, when released, lowers the amount of calcium in the blood.

Inadequate levels of thyroid hormones = hypothyroidism, or Myxedema.

Myxedema symptoms: Facial bloating weakness cold intolerance lethargy altered mental

status oily skin and hair TX: replacement of

thyroid hormone.


Increased thyroid hormone release causes hyperthyroidism, commonly called Graves’ disease. Signs and symptoms:

insomnia, fatigue tachycardia hypertension heat intolerance weight loss

Long term hyperthyroidism: Exopthalmos

bulging of the eyeballs (picture Barbara Bush)

In severe cases - a medical emergency called thyrotoxicosis can result.


Parathyroid Glands small, pea-shaped

glands, located in the neck near the thyroid

usually 4 - number can vary

regulate the level of calcium in the body

produce parathyroid hormone - level of calcium in blood

Hypocalcemia can result if parathyroids are removed or destroyed.


Pancreas a key gland

located in the folds of the duodenum

has both endocrine and exocrine functions

secretes several key digestive enzymes

Islets of Langerhans specialized tissues in

which the endocrine functions of the pancreas occurs

include 3 types of cells: alpha ( ) beta () delta ()

each secretes an important hormone.


Alpha () cells release glucagon, essential for controlling blood glucose levels.

When blood glucose levels fall, cells the amount of glucagon in the blood .

The surge of glucagon stimulates the liver to release glucose stores (from glycogen and additional storage sites).

Also, glucagon stimulates the liver to manufacture glucose -

gluconeogenesis.


Beta Cells () release insulin (antagonistic to glucagon).

Insulin the rate at which various body cells take up glucose. Thus, insulin lowers the blood glucose level.

Insulin is rapidly broken down by the liver and must be secreted constantly.

Delta Cells () produce somatostatin, which inhibits both glucagon and insulin.


Adrenal Glands 2 small glands

that sit atop both kidneys.

Each has 2 divisions, each with different functions.

the Adrenal Medulla secretes the catecholamine hormones norepinephrine and epinephrine (closely related to the sympathetic component of the autonomic nervous system).


The Adrenal Cortex secretes 3 classes of hormones, all steroid hormones: gluticocorticoids

mineralocorticoids androgenic

hormones

One at a time… gluticocorticoids: accounts for 95% of

adrenal cortex hormone production

the level of glucose in the blood

Released in response to stress, injury, or serious infection - like the hormones from the adrenal medulla.


Mineralocorticoids: work to regulate

the concentration of potassium and sodium in the body.

Prolonged in adrenal cortex hormone results in Cushing’s Disease.

Signs & Symptoms of Cushing’s Disease: in blood sugar

levels unusual body fat

distribution rapid mood

swings


And - if there is an in mineralocorticoids as well A serious electolyte

imbalance will occur due to the potassium excretion by the kidney, which results in hypokalemia.

Sodium can also be retained by the kidney, resulting in hyponatremia. Causes:

dysrhythmias coma death

usually results from a tumor - TX? Removal of tumor.


Gonads and Ovaries: the endocrine glands

associated with human reproduction.

Female ovaries produce eggs

Male gonads produce sperm

both have endocrine functions.

Ovaries: located in the

abdominal cavity adjacent to the uterus.

Under the control of LH and FSH from the anterior pituitary they manufacture estrogen protesterone


Estrogen and Progesterone have several functions, including sexual development and preparation of the uterus for implantation of the egg.

Testes: located in the

scrotum produce sperm for

reproduction manufacture

testosterone - promotes male

growth and masculinization

Controlled by anterior pituitary hormones FSH and LH.


Endocrine Emergencies:

Diabetes Mellitus one of the most

common diseases in North America.

insulin secretion by the Beta () cells of the islets of Langerhans in the pancreas.

Complications of Diabetes: contributes to

heart disease stroke kidney disease blindness


Pathophysiology of Diabetes:

Glucose Metabolism Glucose (dextrose) is

a simple sugar required by the body to produce energy.

Sugars, or carbohydrates, are 1 of 3 major food sources used by the body.

The other 2 major food sources are proteins fats

Most sugars in the human diet are complex and must be broken down into simple sugars: glucose, galactose and fructose - before use.


Breakdown of sugars is carried out by enzymes in the gastro intestinal system. As simple sugars,

these are absorbed from the GE system into the body.

More than 95% enter the body as glucose.

To be converted into energy, glucose must first be transmitted through the cell membrane. BUT - the glucose molecule is large and doesn’t readily diffuse through the cell membrane.


Glucose must pass into the cell by binding to a special carrier protein on the cell’s surface. Facilitated

diffusion - doesn’t use energy. The carrier protein binds with the glucose and carries it into the cell.

The rate at which glucose can enter the cell is dependent upon insulin levels. Insulin serves as the

messenger - travels via blood to target tissues.

Combines with specific insulin receptors on the surface of the cell membrane.

cns (central nervous system)

Education

nervous system control

parasympathetic nervous

parasympathetic system

ventricular system

endocrine system

autonomic nervous system

functions brain cerebrum

major parts