Post on 04-Jun-2015
description
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
What are the major parts of the 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
What are the major parts of the nervous system?
2. Peripheral Nervous System
carries all the messages sent between the central nervous system and the rest of the body
What are the major parts of the nervous system?
3. Autonomic nervous system
controls involuntary activity such as the action of the heart and glands, breathing, digestive processes, and reflex actions
What are the major parts of the nervous system?
3. Autonomic nervous system
a. sympathetic system responds to the
body’s needs during increased activity and in emergencies.
controls heartbeat, blood circulation, respiration and other unconscious activities.
What are the major parts of the nervous system?
3. Autonomic nervous system
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
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
a. Cerebrum forms the bulk of the
brain responsible for the
higher thought processes such as memory, judgment and reason
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
a.1Parts of the Cerebrum Frontal lobe planning,
consciousness, speech, memory, and reasoning
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
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
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
a.1Parts of the Cerebrum Occipital lobe contains the centers
responsible for sight.
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
a.1Parts of the Cerebrum Temporal lobe houses centers for the
processing and correlation of the auditory (hearing) and olfactory (smell) senses.
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
b. Cerebellum responsible for body
balance, posture and the coordination of movement
receives, coordinates and modifies orders from the cerebrum
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
c. Brain stem connects the
cerebrum with the spinal cord
consists of the midbrain, pons, and medulla oblongata
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
1. Brain
c. Brain stem pons – located
between the midbrain and the medulla oblangata; connects the cerebellum and the cerebrum
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
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.
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
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
PARTS OF THE CENTRAL NERVOUS SYSTEM AND THEIR FUNCTIONS
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
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.
The Endocrine System
Exocrine glands - transport their hormones to target tissues via ducts.
Endocrine Emergencies: from common:
Diabetes to the unusual:
Thyrotoxicosis
The Endocrine System
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 Endocrine System
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)
The Endocrine System
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.
The Endocrine System
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 Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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 Endocrine 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.
The Endocrine System
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
The Endocrine System
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.
The Endocrine System
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
The Endocrine System
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.
The Endocrine System
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
The Endocrine System
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.
The Endocrine System
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.
The Endocrine System
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.