Stroke

Alzheimer's disease is caused by
​the build-up of proteins called 
 amyloid plaques in the brain.
Another protein called tau forms tangles within brain cells.

bipolar disorder (called also
manic depression) is a condition that exhibits severe high and low mood swings and changes in behavior. it is common f or people with this disorder to feel elated
and energized and then have  periods of feeling hopeless.

0.1% of the population in the US has MS. that number increases to 2.5 to 5%  if you have a sibling or parent with MS. there is a genetic link but factors other than genetics are at play. An identical twin has a 25% chance of developing MS if their twin is affected. 

Alzheimer's disease

reflexes

The thalamus relays >95% of  sensory info to the cortex!
That's all of the vision, taste, touch and balance info but not sensory info from the nose. The olfactory bulb sends that info directly to the cerebrum by the olfactory peduncle.

          the spinal cord

bipolar disorder

protists use chemical signals which were
precursors to neurons and their synapses.

  cingulate gyrus

reflex arc:
a reflex arc consists of a receptor, an integrator and an effector.
sensory cells carry (afferent impulses) to an interneuron in the
spinal cord which sends a response to the motor neuron. 

The fornix is a bundle of nerve fibers that serve as an efferent relay from the hippocampus. The fornix also relays some afferent fibers to the hippocampus from the diencephalon. 

what about neurotransmitter deficiencies?

Research suggests that the
 brains of people with bipolar disorder may differ from the brains of people who do not have this condition. Medical providers
diagnose and treat based on symptoms and history and not
 brain imaging. Research also suggests that bipolar disorder is linked to the presence of specific genes. Individuals who have a parent or sibling with bipolar disorder have an increased chance of having the disorder themselves. 

Most worms have 2 nerve cords running along the length of the body which merge at both ends. These nerve cords are connected by transverse nerves like the rungs of a ladder. These transverse nerves coordinate the two sides of the animal.

Arthropods have a nervous system made up of a series of ganglia all connected by a ventral nerve cord.
Each body segment has one ganglion on each side with the anterior ganglia fused into a brain. Arthropods have well-developed eyes and sensory antennae.

​what is a synapse?

Cnidarians exhibit nerve nets. A nerve nets consist of sensory neurons that pick up chemical/touch signals and motor neurons that can cause contractions.
They also have intermediate neurons serve as a relay system...similar to the ganglia (nerve concentrations) seen in higher order animals.

The Nervous System

neurological disorders include:
multiple sclerosis, Alzheimer's disease, Parkinson's disease, epilepsy, stroke, clinical depression, bipolar disorder

Poriferans do not have neurons hence no nervous system. But they do release Calcium which initiates the contraction of the sponge. 

hypothalamus

​​A nerve impulse is called an 
action potential.

Action potentials are electrical charges that travel along the membrane of a neuron. They start when the neuron's membrane is disturbed by either a mechanical or chemical signal. The cell membrane's potential (the difference in charge across the membrane) changes quickly from negative to positive as Na+ ions flow into the cell. 

 the cingulate gyrus covers the
corpus callosum.
it processes emotions,
regulates behavior regulation and various autonomic motor functions.

pathologies

A stroke occurs when the brain's blood supply is reduced or stopped. this prevents the brain from receiving necessary nutrients/O2 and the brain cells post blockage die. 

types are: hemorrhagic
           ischemic

mammillary bodies/fornix/hippocampus

   thalamus

The hypothalamus serves as a link between the nervous and the endocrine system via the the pituitary gland. Specialized neuron clusters called neurosecretory cells release hormones that direct the pituitary gland to in turn release hormones.
Example:
the hypothalamus secretes thyrotrophin releasing hormone (TRH). This triggers the pituitary gland to secret thyroid stimulating hormones (TSH) which is released into the blood. The thyroid gland has receptors for this hormone which informs the thyroid gland to release thyroid hormone. Thyroid hormones are essential for metabolic homeostasis. See the negative feedback loop to the right. Other hormones released by the hypothalamus include corticotrophin-releasing hormone, dopamine, growth hormone-releasing hormone, somatostatin and gonadotrophin-releasing hormone. 

multiple sclerosis/MS

at a synapse, chemicals called neurotransmitters are released from the end of a neuron, travel across the synapse, and bind to receptors on an adjacent neuron. This initiates the action potential at this next neuron. In this way, the signal in  the form of t he action potential travels from neuron to neuron
OR
from neuron to muscle cell or glandular cell. 

 hypothalamus and stress...

The thalamus is located just above the brain stem between the cerebral cortex and the midbrain. It serves to relay motor and sensory info to the cerebral cortex as well as regulating alertness/wakefulness and sleep. 
​The spinothalamic tract is a sensory pathway that originates in the spinal cord, relaying info to the thalamus about discomfort ie...itch, temperature...pain. 

evolution of the nervous system

                       the brain

​what is a nerve impulse...

aka action potential?

cingulate gyrus helps to regulate our response to fearful or unpleasant experiences and the prediction and avoidance of negative consequences associated with these stimuli.  it serves to help us avoid  negative stimuli via the recall of associated memories. 

it shares extensive neural pathways with other brain regions so it is often considered a "connecting hub of emotions, sensation, and action" along with regulating executive functions, motor control, memory, and learning. 

Parkinson's disease is a neurodegenerative disorder that affects dopaminergic (dopamine producing) neurons.  the cause is unknown. Alpha-synuclein is a protein found in these neurons. In PD,  the protein folds incorrectly and results in clumps called Lewy Bodies. The current hypothesis is that Lewy bodies are toxic to these neurons and may even get passed along from one neuron to the next which causes the spread of the disease. 

Nerve cords are seen in bilateral animals. The nerve cord has a large ganglion at the front we commonly call the brain. Segmented animals exhibit smaller ganglia along their bodies. Our spinal cord contains a series of segmental ganglia. 

There's a difference between  nerve cord placement depending on embryonic development:
protostomes have a ventral nerve cord.
deuterostomes have a dorsal nerve cord.

Clinical depression

Parkinson's disease

The mammillary bodies are part of the diencephalon. paired mammillary bodies are found on the inferior surface of the hypothalamus.  Serving as relay nuclei, they forward information from the hippocampus to the thalamus to aid in memory consolidation. 

          CSF

As the primary efferent tract of the hippocampus, the fornix relays information from the hippocampus to the mammillary bodies and on to the to the thalamus.

There's a third system not mentioned in this diagram...

the enteric nervous system (ENS), a network of nervous tissue located in the walls of the digestive tract. It coordinates many visceral activities without the direction of the CNS although the ANS does exert some influence over this system. There are as many neurons in the ENS (1 x 10*8) as the spinal cord and this system uses familiar neurotransmitters, such as serotonin which plays a vital role in the gut and brain connection. 

         here's the bottom line...
​   receptor > integrator > effector
   (afferent)                         (efferent)
   (sensory)                           (motor)

There is an inherited predisposition to developing depression. depression can also be caused by physical illness, aging and  gender.

Depression can manifest as temporary episodes of sadness all the way up to persistent depression. major depression or major depressive disorder is also called clinical depression. it's different from being depressed due to an episodic event such as a death in the family. This severe form of depression is diagnosed using the APA's Diagnostic and Statistical Manual of Mental Disorders (DSM-5)

The mammillary bodies are associated with recall/memory. Recall begins in with the activation of neurons in the hippocampus. memories
are relayed through the fornix to the mammillary bodies 

Although MS is an autoimmune disease, the cause of multiple sclerosis is unknown. Both genetics and environmental factors are thought to be responsible. there are associated risk factors including:
sex: twice as may women as men are affected
family history of the disease
infections: several viruses including Epstein-Barr, have been related to onset
race: those of Northern European descent are at highest risk 
climate. MS is more common in  areas with temperate climates
vitamin D: low levels of vitamin D/
low exposure to UV
other autoimmune diseases

MS = multiple sclerosis
is an autoimmune disease whereby the immune system degrades myelin. this causes nerve relay problems between the CNS and PNS and a deterioration of nerves.
symptoms of MS vary, depending  on the level of damage and the # of nerves affected. although there isn't a cure for MS, there are therapeutics which can manage symptoms. 

The presence of a central nervous system (CNS) is a huge leap in the evolution from invertebrates to vertebrates. A group of genes duplicated early in vertebrate evolution. These duplicate genes are differentially expressed in the CNS. In lower vertebrates, the surfaces of the brain have a smooth surface. But mammal brains have grooves and undulations which offered a considerably larger surface for the same volume. The surface of the brain (cerebral cortex) is where the bodies of neurons sit...
the more grooves and convolutions the brain has, the larger its cortex, the larger the number of neurons.
It is more efficient!

​





​The brain of a crocodile is larger than a brain of a mouse. But the cerebral cortex of the mouse is larger than that of the crocodile = mouse is "smarter".

The hippocampus is a  embedded deep into temporal lobe and plays a central role in learning and memory.

so neurotransmitters...?