Nervous System Flashcards
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Nervous system functions
Functions:
-Sensory functions.
-Integrating functions.
-Motor functions.
-The study of the nervous system and its parts is called neurology.
Neuron parts
Dendrite: Receives stimuli/impulses and conduct to the cell body.
Axon: Conduct nerve impulses away from the body toward another neuron or effector cell.
Myelin sheath: The cell membranes of specialized glial cells.
Schwann cell: Cells in the peripheral nervous system that form the myelin sheath around a neurons axon.
Nucleus: contains the genetic material (chromosomes) of the neuron cell.
Axon terminal: The portion of the neuron that releases the impulse to the adjoining neuron or cell AKA terminal bouton.
Node of ranvier: Works together with the myelin sheath to increase the speed of conduction of impulses along the axon.
Afferent nerves
toward from the CNS - aka sensory nerves.
Efferent nerves
away from the CNS aka motor nerves.
Autonomic VS Somatic.
Somatic refers to voluntary actions like a dog turning its head when its called.
Autonomic refers to the subconscious involuntary actions of an animal such as heartbeat and hormone production.
How do nerves work?
⦿ The cell membrane of the neurons are electrically charged, even at rest - resting state
-The charge of the cell will vary depending on the phase of polarization.
Resting Cell
⦿ Na+ (sodium) doesn’t naturally diffuse through the cell membrane.
⦿ Na+ (sodium) accumulates on the outside of the cell.
⦿ Maintains an overall positive charge on the outside of the cell membrane.
⦿ K+ (potassium) doesn’t naturally diffuse outside the cell membrane.
⦿ Cl- (chloride) and COO- (carboxylate) hang out inside the cell with K+ (potassium)
⦿Positive outside the cell membrane, negative inside the cell membrane.
When there are negative elements against positive elements that refers to them being “polarized”
Resting Membrane Potential
⦿ The electrical differences across the cell membrane. = negative charge inside.
Impulse Connects with the dendron and enters the sodium and potassium channels, The impulse travels into the neuron and Na+ allow only other Na+ to flow into the cell.
⦿ In neurons, the rapid rise in potential, depolarization, is an all-or-nothing event that is initiated by the opening of sodium ion channels within the plasma membrane. The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels.
Repolarization
⦿ Instantly the Na+ channels snap shut.
⦿ K+ channels open.
⦿ K+ escapes the cell.
⦿ This rush of K+ ions out of the neuron cause a swing back to the cell being negatively charged.
⦿ Negative charge inside the cell has been restored.
⦿ But…
-Now the K+ ions are outside the cell membrane.
-The Na+ ions are inside.
-How to restore the balance of these ions.
-Sodium/potassium pump.
Whereby the sodium channels close and the potassium channels open and potassium shifts to outside the cell, now its going back to negative on the inside and positive on the outside.
Resting state
Is the polarized state where the sodium is outside the cell membrane potassium is inside the cell membrane it is a general negative charge inside the cell thanks to the chloride and carboxylate which are negatively charged, this is considered polarized.
Depolarization
Nerve influx comes through the cell, comes through the dendrite passes through the cell body, as its passing through the sodium gates will open and allow that influx of sodium to get into the cell, that screws up the balance and makes the inside of the cell very positive as well as the outside of the cell which is also positive.
Refractory period
The refractory period is when the neuron is in the midst of depolarization process and is unable to respond to another stimuli
Final Stage
the final stage is where the Sodium-Potassium pump redistributes the sodium to the outside of the cell and potassium to the inside of the cell.
Depolarization Threshold
Not all signals will be strong enough to cause the neuron to depolarize.
⦿ Weak signals may cause just a bit of Na+ to enter the cell.
⦿ At which time the Na+ pump would simply place the back outside the cell.
⦿ Neuron goes back to resting state, the impulse was not sent to the brain.
⦿ Depolarization Threshold, the stimulus is strong enough to cause depolarization.
Conduction of nerve impulse
⦿ Conduction of action potential.
⦿ Wave of depolarization.
⦿ Essentially when Na+ Channels start opening it causes a wave effect of more Na+ channels opening, which is the nerve impulse creation.
All or Nothing.
⦿ Myeline sheaths allow for depolarization to happen fast, the wave of depolarization to happen faster.
⦿ The nodes of Ranvier are gaps along the myelin sheath that covers the axon of neuron cells. They function to recharge the action potential that runs along the axon.
Synapses and Boutons
⦿ Nerves are anti-social they do not touch eachother.
⦿ Instead there is a gap (synapse) between each of the nerves.
⦿ The terminal portion of the axon (bouton) and the target cell or another neuron connect together via the synapse.
⦿ Impulse is sent through the terminal bouton.
⦿ Vesicle of the neurotransmitters is released and diffused into the post synaptic cell.
⦿ Post synaptic membrane = receptors.
⦿ Receptors = very selective. each receptor is very selective to different types of neurotransmitters.
Neurotransmitters: (Exciatory or inhibitory)
⦿ Exciatory: Encourage depolarization by creating an influx of Na+ into the cell to help it move toward the threshold.
⦿ Inhibitory: Hyperpolarize the cells to maintain negative charge on the inside of the cell.
⦿ Example:
⦿ Benzodiazepines enhance the effect of GABA, the main inhibitory neurotransmitter.
⦿ GABA opens Cl- channels in neurons.
⦿ Negatively charged neuron = less likely to fire.
⦿ Result: tranquilizer effect.
Types of Neurotransmitters
⦿ Acetylcholine- Can be both inhibitory and exciatory.
⦿ Norepinephrine- Arousal, fight or flight sympathetic NS.
⦿ Epinephrine- Released by the adrenal gland, acts as a hormone as part of the fight or flight response.
⦿ Dopamine- involved in autonomic functions and muscle control.
⦿ GABA- Gamma-aminobutyric acid- inhibitory effect- tranquilization.
BRAIN: Central Nervous System (CNS): Parts:
-Cerebrum
-Cerebellum
-Diencephalon
-Brain stem
⦿ Spinal Cord.
Cerebrum
In veterinary medicine, the cerebrum plays a crucial role in understanding various aspects of animal behavior, neurology, and pathology. The cerebrum is the largest part of the brain in mammals, including animals, and it is responsible for higher cognitive functions such as thought, perception, memory, and decision-making. Understanding the anatomy and function of the cerebrum is essential for diagnosing and treating neurological disorders in animals.
Gyri (gyrus)
Gyri (singular: gyrus) are the folds or convolutions of the cerebral cortex, the outermost layer of the cerebrum, in the brain. They are often referred to as the “bumps” or “ridges” on the brain’s surface. The gyri significantly increase the surface area of the cerebral cortex, allowing for more extensive neuronal connections and higher cognitive functions.
Fissures
Fissures are deep grooves or furrows that divide the brain’s surface into lobes or separate larger regions. They are the natural boundaries that help organize the brain’s structure and separate different functional areas. Fissures are often deeper than sulci, which are shallower grooves on the brain’s surface.
Sulci (Sulcus)
Sulci (singular: sulcus) are shallow grooves or furrows on the surface of the brain, particularly in the cerebral cortex. They are the counterpart to gyri, which are the raised folds or ridges on the brain’s surface. Sulci play important roles in increasing the brain’s surface area, allowing for more extensive neuronal connections within a confined space, and they also serve as landmarks for identifying different functional areas of the brain.
Longitudinal fissure
The longitudinal fissure is a deep groove that runs along the midline of the brain, separating the left and right cerebral hemispheres. It is one of the most prominent and defining features of the brain’s anatomy.
Cerebellum
The cerebellum, located at the back of the brain, underneath the cerebral hemispheres, plays a crucial role in motor control, coordination, balance, and some cognitive functions. It is divided into two hemispheres with a folded surface of gyri and sulci, composed of gray matter on the outside and white matter on the inside. The cerebellum receives input from various parts of the brain and spinal cord, integrating sensory information to fine-tune and coordinate muscle activity for smooth movements and posture maintenance. It contributes to motor learning, skill acquisition, and certain cognitive functions such as attention and language processing. Damage or dysfunction of the cerebellum can lead to ataxia, tremors, balance problems, and other neurological deficits. Diagnosis involves neuroimaging techniques like MRI or CT scans, and treatment may include physical therapy, medications, or surgical intervention depending on the underlying cause.
Cerebellar Hypoplasia
Cerebellar hypoplasia is a neurological condition characterized by underdevelopment or incomplete development of the cerebellum, the part of the brain responsible for motor coordination and balance. It results in a smaller-than-normal cerebellum with fewer neurons and impaired function, with causes including genetic factors, prenatal exposure to toxins or infections, maternal drug or alcohol use during pregnancy, or developmental abnormalities. Symptoms include difficulties with motor coordination, balance, walking, fine motor skills, tremors, and involuntary movements. Diagnosis involves imaging studies such as MRI or CT scans. Treatment focuses on managing symptoms with physical therapy, occupational therapy, speech therapy, and medications. Prognosis varies depending on the severity of the condition, but early intervention can help manage symptoms and improve quality of life.
Diencephalon
The diencephalon, located between the cerebral hemispheres and the brainstem, comprises the thalamus, hypothalamus, epithalamus, and subthalamus. The thalamus relays sensory information to the cerebral cortex, while the hypothalamus regulates physiological processes, behaviors, and the autonomic nervous system. The epithalamus, primarily the pineal gland, secretes melatonin to regulate the sleep-wake cycle and other functions. The subthalamus is involved in motor control and is connected to the basal ganglia. Dysfunction can lead to sensory deficits, sleep disturbances, hormonal imbalances, and movement disorders.