Nervous System, Lourdes Llamas, Period 1 (Major nerves of the body…
Nervous System, Lourdes Llamas, Period 1
Diseases associated with the brain
Parkinson's disease- results from a degeneration of the dopamine-releasing neurons of the substantia nigra. As those neurons deteriorate, the dopamine-deprived basal nuclei they target become overactive. Patients have a persistent tremor at rest, a forward-bent walking posture and shuffling gait, and a stiff facial expression.
Alzheimer's disease- a progressive degenerative disease of the brain, ultimately results in dementia.AD patients represent nearly half of the people living in nursing homes.They exhibit memory loss, shortened attention span, disorientation, and eventual language loss.
Huntington's disease- a fatal hereditary disorder, strikes during middle age. Mutant huntington protein accumulates in the brain cells and the tissue dies, leading to massive degeneration of the basal nuclei and later of the cerebral cortex.
Major divisions and subdivisions of the nervous system
The central nervous system- consists of the brain and spinal cord, which occupy the dorsal body cavity and is the integrating and control center of the nervous system
The peripheral nervous system- part of nervous system outside the CNS.Consists of spinal nerves that carry impulses to and from the spinal cord and cranial nerves which carry impulses to and from the brain.
Subdivision: The sensory- somatic and visceral sensory nerve fibers conduct impulses from receptors to the CNS
Subdivision: The motor(efferent)- consists of motor nerve fibers that conduct impulses from the CNS to effectors(muscles and glands)
Their are 31 pairs of spinal nerves : 8 pairs of cervical nerves (C1-C8) , 12 pairs of thoracic nerves (T1-T12), 5 pairs of lumbar nerves (L1-L5), 5 pairs of sacral nerves (S1-S5), and 1 pair of tiny coccygeal nerves (C0)
Anatomy of the spinal cord
The spinal cord is protected by bone, meninges, and cerebrospinal fluid. The single-layered spinal dura mater is not attached to the bony walls of the vertebral column.Between the bony vertebrae and the spinal dura mater is an apideral space filled with soft padding of fat and network of veins. Inferiorly, the spinal cord terminates in a tapering cone-shaped structure called conus medullaris. The filum terminale, a fibrous extension of the conus medullaaris to the cocyx, where it anchors the spinal cord so it is not jostled by body movements. Spinal card has enlargements called cervical and lumbar. The spinal cord is somewhat flattened from front to back and two grooves mark it's surface:the wide ventral median fissure and the narrower dorsal median sulcus.
Major functions of the nervous system
Integration- The nervous system processes and interprets sensory input and decides what should be done at each moment
Motor input- The nervous system activates effector organs(muscles and glands) to cause a response
Sensory input- nervous system uses millions of sensory receptors to monitor changes occurring both inside and outside the body
Classification of neurons
Structural classification- grouped neurons according to the number of processes extending from their cell body
Bipolar neurons- have two processes-an axon and a dendrite that extend from opposite sides of the cell body.
Unipolar neurons- have a single process that emerges from the cell body and divides T-like into proximal and distal branches.
Multipolar neurons- have three or more processes- one axon and the rest dendrites. Most common type in humans.
Functional classification- groups neurons according to the direction in which the nerve impulses travels relative to the central nervous system.
Motor or efferent neurons- carry impulses away from the CNS to the effector organs(muscles and glands) of the body.
Interneurons- lie between motor and sensory neurons in the neural pathways and shuttle signals through CNS pathways where integration occurs.
Sensory or afferent neurons- transmit impulses from sensory receptors in the skin or internal organs toward or into the central nervous system.
Drugs that affect the brain
Methamphetamine- the neurotransmitter, dopamine, interferes with this drug by the excess dopamine causing transporters to start working in reverse and also pumps dopamine out of the cell.A person is affected with intense pleasure and exhilaration.
Alcohol- the neurotransmitter,GA BA/inhibitory and glutamate, interferes with the drug by acting acting to control neural activity along many brain pathways.A person is affected with unstableness and impulse control.
Marijuana- the neurotransmitter, inhibitory, interferes with the drug by the carabinoid receptors turning off the release of inhibitory neurotransmitters. A person is affected with short term memories and feeling relaxed.
Cocaine- the neurotransmitter, dopamine, interferes with the drug by the receptors over stimulating the cell. A person is affected by being nervous and unable to be still.
Ecstasy- the neurotransmitter, serotonin, is affected by this drug by it's transports being "confused" and someones actions are also affected such as their mood, sleep, perception, and appetite.
LSD- the neurotransmitter, serotonin, interferes with the drug by binding to other serotinin receptors. A person is affected with hallucinations.
Heroine- the neurotransmitters, dopamine and inhibitory, are affected by heroine by inhibiting dopamine from being released.A person is affected by this drug for it being a pain killer to stress and emotion.
Layers of the Meninges-
Arachnoid mater- The middle meninx, forms a loose brain covering, never dipping into the sulci at the cerebral surface. It is separated from the dura mater by a narrow serous cavity.
Pia mater- is composed of delicate connective tissue and contains many tiny blood vessels. It is the only meninx that clings tightly to the brain like plastic wrap, following it's every convolution.
Dura mater- The leathery dura mater is the strongest meninx and surrounds the brain. It is a two layered sheet of fibrous connective tissue
Tissues (structure and function of a neuron)
Neuron cell body- consists of a spherical nucleus surrounded by cytoplasm.The cell body is the major biosynthetic center and metabolic center of a neuron. It also contains many other structures such as protein- and membrane- making machinery, cytoskeletal elements, and pigment inclusions.
Neuron processes- extend from the cell body of all neurons and their are two types which are dendrites and axons.Dendrites of motor neurons are short, tapering, diffusely branching extensions. A neuron never has more than a single axon. The axon arises from a cone-shaped area of the cell body called axon hillock.
Neuron- are the structural units of the nervous system. They are high specialized cells that function to conduct messages in the form of nerve impulses from one part of the body to another. Their characteristics include excitability, have extreme longevity, are amitotic, and have exceptionally high metabolic rate.
Spaces and ventricles-
Third ventricle- Each lateral ventricle communicates with the narrow third ventricle in the diencephalon via a channel called an interventricular foramen.
Cerebral aqueduct- canal-like that runs though the midbrain
Fourth ventricle- lies in the hindbrain dorsal to the pons and superior medulla.It is continuous with the central canal of the spinal cord inferiorly. Also connects with the central canal
Cerebrospinal fluid- clear watery fluid that fills the space between the arachnoid membrane and the pia mater
Lateral ventricle- Their is one deep within each cerebral hemisphere , are large C-shaped chambers that reflect the pattern of cerebral growth. Consists of spaces such as the anterior horn, posterior horn, and the inferior horn. .
Major parts and functions of the spinal cord
Function- the white spinal cord provides a two-way conduction pathway to and from the brain.The spinal reflexes are initiated and completed at the spinal cord level.
The spinal cord is separated by the cervical, thoracic, and lumbar regions. The spinal cord terminates in a tapering cone-shaped structure called the conus medullaris. The filum terminale, a fibrous extension of the conus covered by pia mater.The spinal cord has 31 pairs of spinal nerves that attach to the cord by paired roots.The spinal cord is somewhat flattened from front to back and two grooves mark it's surface:the wide ventral median fissure and the narrower dorsal median sulcus.
Major part of the brain and their functions
Cerebellum- is located under the cerebrum and functions to coordinate muscle movements, maintain posture, and balance
Brainstem- acts as a relay center connecting the cerebrum and cerebellum to the spinal cord. It functions to do many automatic things such as breathing, body temperature, digestion, sneezing, coughing, and much more.
Cerebrum- is the largest part of the brain which is composed of left and right hemispheres and functions with interpreting touch, vision, hearing, speech, reasoning, emotions, learning, and many more high functions.
Diencephalon- relays sensory information between brain regions and controls many autonomic functions of the peripheral nervous system.
Lobes of the brain and their functions
Parietal lobe- is located in the middle section of the brain and is associated with processing tactile sensory information such as pressure, touch, and pain.
Temporal lobe- is located at the sides of the brain and is associated with primary auditory perception, such as hearing, receives sensory information from the ears and secondary areas to process the information into speech and words.
Frontal lobe- is located at the front of the brain and is associated with reasoning, motor skills, high level cognition, and expressive language.
Occipital lobe- is the visual processing center containing most of the anatomical region of the visual cortex.
An action potential is a brief reversal of membrane potential with a total amplitude(change in voltage) of about 100 mV(from -70 mV to +30 mV). The resting state is when no ions move through voltage-gated channels. Depolarization is caused by Na+ flowing into the cell. The repolarization is caused by K+ flowing out of the cell. Hyperpolarization is caused by K+ continuing to leave the cell.
Threshold-is the membrane potential at which the outward current created by K+ movement is exactly equal to the inward current created by Na+ movement.Threshold is reached when depolarized by 15 to 20 mV from the resting value.
Propagation- An AP must be propagated along the axon's entire length.At 2ms, action potential reaches the recording electrode.At 4 ms, action potential peak has passed the recording electrode.Membrane at the recording electrode is still hyperpolarized.
Compare and contrast the Autonomic nervous system
Autonomic nervous system has different cell bodies such as parasympathetic and sympathetic while the somatic nervous system only has one .The autonomic system has a lightly myelinated preganglionic axon while the somatic nervous system has a heavily myelinated axon.Autonomic has a neurotransmitter effector of both NE and ACh while somatic only has ACh.Lastly, the autonomic system has effector organs including smooth muscles, glands, and cardiac muscle while the somatic only has the skeletal muscle.
Cerebrospinal fluid(CSF)- Found in and around the brain ans spinal cord, forms a liquid cushion that gives buoyancy to CNS structures. CSF effectively reduces brain weight by 97% and prevents the delicate brain from crushing under its own weight.
Blood brain barrier- is the protective mechanism that helps maintain the brain's stable environment.
Meninges-are three connective tissue membranes that lie just external to the CNS organs. These meninges cover and protect the CNS and these three include dura mater, pia mater, and arachnoid mater.
Major nerves of the body
Divisions of the PNS of the body
Sensory (afferent) division- somatic and visceral sensory nerve fibers conduct impulses from receptors to the central nervous system
Motor (efferent) division- motor nerve fibers conduct impulses from the CNS to effectors (muscles and glands)
Somatic nervous system- somatic (voluntary) motor nerve fibers conduct impulses from the CNS to skeletal muscles.
Autonomic nervous system(ANS)- visceral (involuntary) motor nerve fibers conduct impulses from the CNS to cardiac muscle, smooth muscle, and glands.
Sympathetic division- mobilizes body systems during activity
Parasympathetic division- conserves energy and promotes house-keeping functions during rest.
Componets include: 1)Receptor:site of stimulus action 2)Sensory neuron:transmits afferent impulses to CNS 3)Integration center:either monosynaptic or polysynaptic region within CNS 4)Motor neuron:conducts efferent impulses from integration center to effector organ 5)Effector: muscle fiber or gland cell that respondsto efferent impulses by contracting or secreting.
Reflexes are classified functionally as somatic reflexes (activate skeletal muscle) and autonomic reflexes (activate visceral effectors)
Gases and lipids-small, short-lived, toxic gas molecules
Peptides- include a broad spectrum of molecules with diverse effects.
Biogenic Amines- include the catecholamines such as dopamine, norepinephrine (NE), and epinephrine, and the indolamines, which include serotonin and histamine.They play role in emotional behavior and help regulate biological clock.
Amino Acids- include glutamate,aspartate, glycine, and gamma, and many others. It is very difficult to know this neurotransmitters role since amino acids occur in all cells of the body and are important in many biochemical reactions.
Acetylcholine (ACh) - is still best understood because it is released at neuromuscular junctions, which are much easier to study.It is released by all neurons that stimulate skeletal muscles and by many neurons of the autonomic nervous system.
Purines- are one of the classes of nitrogen-containing bases that make up DNA and RNA. Two purines, ATP and adenosine, also have well-established roles as chemical messengers:Adenosine triphosphate (ATP) and adenosine.