A&P Chapters 12, 13, 14 Nervous System Flashcards
What are the two systems that allow organs and tissues to communicate with each other and coordinate homeostasis?
The Endocrine and Nervous Systems
What does the nervous system do?
Acquires information: Sense receptors in tissues and organs send (afferent) information to the brain and spinal cord.
Processes information: The Brain and Spinal cord determine what action (if any should be taken).
Initiates action: Brain and spinal cord send messages that cause muscles, organs or tissues to carry out some action.
What advantages does the Nervous system have over the Endocrine system?
The nervous system can be very targeted and can be stimulated rapidly. The endocrine system is slower and can’t be as targeted.
What are the neurons called that process information in the CNS from afferent neurons?
Interneurons
What are the two ANATOMICAL divisions of the nervous system?
Central Nervous System: The Brain and Spinal Cord
Peripheral Nervous System: All the nerves and ganglia not part of the CNS
What body cavity is the CNS located?
The Dorsal Body Cavity
Define NERVES
A Bundle of neuronal axons wrapped up in connective tissue.
Define GANGLION
A swelling or enlargement of a nerve where the cell bodies (soma) are located.
What are the FUNCTIONAL divisions of the Nervous system?
The Sensory Division and the Motor Division
Describe the Sensory Division of the Nervous System
The sensory division receives information and transmits it to the CNS via AFFERENT NEURONS
Describe the Motor Division of the Nervous System
The Motor division sends signals from the CNS to muscles, glands, organs, ect… these are EFFERENT NEURONS
What are the subdivisions of the Sensory and Motor divisions?
The Visceral and Somatic Divisions
Describe Somatic
It refers to the skin, muscles, joints and bones.
Describe Visceral
It refers to internal organs like the heart, lungs, liver, stomach, ect….
Which division of the Nervous system is the Sympathetic and Parasympathetic divisions found?
The Visceral Motor division of the Peripheral Nervous System.
Describe Visceral Sensory
It receives information from internal organs and sends that information to the CNS
How fast is the heart beating? How full is the stomach?
Describe Somatic Sensory
Receives information from bones, joints, skin and muscles then transmits it to the CNS.
Touch, pressure, hot/cold, pain, ect…
Describe Visceral Motor
Carries signals from the CNS to internal organs.
Increase/decrease heart rate, trigger release of gland secretions, alter contraction of smooth muscle.
This is all done unconsciously, this is the AUTONOMIC NERVOUS SYSTEM.
Describe Somatic Motor
Carries signals from the CNS to muscles/skin.
Contraction of skeletal muscle
What is the AUTONOMIC NERVOUS SYSTEM?
The system that is related to the visceral sensory and motor divisions. Information received from the visceral sensory division is processed and signals are sent to organs via the visceral motor division.
The ANS is very important for regulating the functions of many organ systems.
What are the two divisions of the Autonomic Nervous System?
The Sympathetic and Parasympathetic
Describe the Sympathetic Division of the ANS
It stimulates the fight or flight response, using Norepinephrine as a neurotransmitter.
It prepares the body for activity, increases the heart rate, blood pressure, respiratory rate, blood glucose levels, dilates pupils ect…
The Sympathetic division also decreases the function of the digestive system.
Describe the Parasympathetic Division of the ANS
Generally slows down many body functions. The Rest and Digest response.
Decreases heart rate, decreases respiratory rate, increases the activity of the digestive system.
What are the two main structures of the CNS?
Brain and Spinal Cord
What are the 3 main parts of the brain?
Cerebrum, Cerebellum, and Brainstem
What are GYRI?
The folds of brain tissue.
What are SULCI?
The grooves in the brain tissue.
What does ROSTRAL refer to?
Anterior
What does CAUDAL refer to?
Posterior
What structures make the Brainstem?
The Midbrain, Pons and Medulla oblongata
What cranial fossa does the Cerebellum lie?
The Posterior Cranial Fossa
What structure divides the Cerebrum into the Right and Left Hemispheres?
The Longitudinal Fissure
What are the four lobes of the Cerebrum?
Frontal, Parietal, Temporal and Occipital
Describe the Frontal Lobe
Responsible for voluntary motor function, memory, mood, emotion and planning. Separated from the Parietal lobe by the Central Sulcus. It contains the Precentral Gyrus
Describe the Parietal Lobe
Responsible for Sensory reception, taste, and some visual processing. Separated from the frontal lobe by the central sulcus, separated from the temporal lobe by the lateral sulcus/fissure and separated from the occipital lobe by the parieto-occipital sulcus.
Describe the Temporal Lobe
Responsible for hearing, smell, learning, memory, some vision processing and emotion. Separated from the parietal lobe by the lateral sulcus.
Describe the Occipital Lobe
The Primary area for vision. Seprated from the parietal lobe by the parieto-occipital sulcus.
Describe the Precentral Gyrus
Located in the Frontal Lobe of the Cerebrum. Important for coordinating and initiating motor control.
Describe the Postcentral Gyrus
Located in the Parietal Lobe of the Cerebrum, Important for processing sensory information. Somatic sensory information is processed in the Postcentral Gyrus.
Where is Somatic sensory information processed?
In the Postcentral Gyrus
Describe Gray Matter
It primarily consists of neuronal dendrites, soma, and synapses.
Describe White Matter
It primarily consists of bundles of Axons (TRACTS) connecting one part of the brain to another.
What surrounds the AXONS to make them appear white?
Myaline
What is the outer layer of Gray matter called in the Cerebrum?
The Cerebral Cortex
What does the Cerebral Cortex do?
It carries out higher level brain functions that separates humans from lower primates. Many areas of the cerebral cortex have specialized functions.
What does DECUSSATE mean?
It describes the crossing over of tracts from one side of the body to another. So sensory information from the left side of the body is processed by the right side of the brain.
Describe the Cerebellum
It is the second largest part of the brain. It has a right and left hemisphere like the Cerebrum. It has much more Gray matter than White. The White Matter of the Cerebellum is called the Arbor Vitae.
It is important for processing many types of sensory signals received from all over the body.
It contains 50% of the neurons of the brain but takes up only 10% of the brains volume.
Describe the Corpus Callosum
A Thick bundle of nerve fibers linking the hemispheres of the Cerebrum.
Describe the Thalamus
It is a relay center in the brain that receives information and directs it to the different area of the Cerebrum.
Describe the Hypothalamus
It is the major control center for the AUTONOMIC NERVOUS SYSTEM AND ENDORCINE SYSTEM.
Very important for relaying messages to the Pituitary Gland.
It contains sensory neurons for Blood Glucose levels, Blood Calcium levels, ect…
Describe the Pituitary Gland
The “master gland” of the body. The Pituitary Gland receives information from the hypothalamus and secretes hormones that control the actions of many other glands in the body.
Describe the Midbrain
Connects the Cerebrum, Cerebellum, Pons, and Medulla oblongata.
It helps coordinate some visual and auditory reflexes.
Describe the Pons
Conducts signals between the Cerebrum and Cerebellum.
Sends sensory messages to the Thalamus.
Describe the Medulla oblongata
Conducts motor signals from the Cerebrum to the spinal cord and sensory signals from the spinal cord to all other parts of the brain.
Contains regions which control cardiovascular and respiratory systems as well as reflexes like coughing and sneezing.
What are the MENINGES?
The layers of connective tissue that surrounds the brain and spinal cord.
The MENINGES play an important role in protecting the brain.
What are the layers of MENINGES?
Dura mater, Arachnoid mater, and Pia mater.
What are the spaces between the layers of MENINGES?
Epidural space, Subdural Space, and Subarachnoid space
What are the two layers of Dura mater?
The Periosteal layer and the Meningeal layer.
What structure does the Periosteal layer of the Dura mater connect to?
The Periosteum of the skull bones.
What layer comprises the Falx Cerebri and what structures does it separate?
It is comprised of the Meningeal layer of the Dura mater.
It separates the right and left hemispheres of the Cerebrum through the Longitudinal Fissure.
What layer comprises the Tentorium Cerebelli and what structures does it separate?
It is comprised from the Meningeal layer of the Dura mater.
It separates the Cerebellum from the Cerebrum.
Describe the Arachnoid mater
The Middle layer of the meninges that is important for cushioning of the brain. Tiny extensions give the layer a spider like appearance. CSF is found in the subarachnoid spaces between the arachnoid mater and the pia mater.
Describe the Pia mater
The innermost, thinnest layer of meninges. It is a very thin layer of connective tissue that follows the contours of the gyri and sulci of the brain.
Describe Cerebrospinal fluid
It is a specialized fluid that is found within ventricles and surrounding the brain in the subarachnoid space.
It is produced by choroid plexuses within the ventricles.
The Ependymal cells lining the ventricles and within the subarachnoid space move the CSF with cilia.
What are the functions of CSF?
Buoyancy; the brain is suspended in CSF. It allows the brain to reside the crainial cavity without its own weight damaging it.
Protection; CSF acts as a shock absorber when the head receives a blow.
Chemical Stability; CSF is eventually reabsorbed into the bloodstream allowing metabolic wastes to be easily removed from the nervous system.
Where is the Cerebrospinal fluid reabsorbed at?
It is reabsorbed into the venous blood supply through small extensions of the Arachnoid mater called ARACHNOID VILLI or GRANULATIONS
Describe the path of CSF from production to reabsorption.
The CSF is produced within the lateral ventricles by the choroid plexuses.
The CSF travels from the Lateral ventricles through the INTERVENTRICULAR FORAMEN to the Third Ventricle, from the third ventricle it travels down the CEREBRAL AQUEDUCT to the Fourth Ventricle.
From the Fourth ventricle it enters the Subarachnoid space through the two lateral apertures and the median aperture.
It is then reabsorbed into the venous bloodstream through the arachnoid villi or granulations.
What are the functions of the Spinal Cord?
Conduction; acts as an information highway that allows communication between the brain and the rest of the body.
Locomotion; although the brain controls the initiation, speed and direction of walking, the spinal cord is responsible for generating the repetitive motor signals that coordinate walking.
Reflexes; involved in the processing and execution of motor responses due to certain stimuli. Knee and elbow reflexes are good examples.
Describe Spinal Cord Anatomy
It consists of a long cylinder of nervous tissue extending from the Foramen Magnum to the 1st Lumbar Vertebrae occupying only the upper 2/3’s of the vertebral column.
The spinal cord gives rise to 31 pairs of spinal nerves that exit through intervertebral foramen and travel to all muscles and tissues of the body.
Spinal nerves continue to travel down the vertebral column past the end of the spinal cord and exist as a bundle of nerves called the CAUDA EQUINA
The spinal cord is covered by the same three layers of meninges as the brain. The Dura mater, Arachnoid mater and the Pia mater.
Describe the CAUDA EQUINA
It is the bundle of spinal nerves that extend past the spinal column. The Pia mater ends at the CONUS MEDULLARIS and so the CAUDA EQUINA is surrounded by the Arachnoid mater and the Dura mater.
Where is the Gray and White matter in the brain? Where is it in the Spinal Cord?
The Gray matter is on the outside and the White is on the inside of the Brain.
The Gray is on the inside and the White is on the outside in the Spinal Cord.
What are Tracts?
Large numbers of axons bundled together in the spinal cord.
Describe Ascending tracts
Bundles of axons carrying SENSORY (AFFERENT) information TO the Brain.
Typically involves 3 neurons. 1st order from the tissue, muscle or organ to the spinal cord or brainstem. 2nd order carry info from the 1st to the THALAMUS which sorts the info and sends it onto other parts of the brain via the 3rd order neurons.
Describe Descending tracts
Bundles of axons carrying MOTOR (EFFERENT) information FROM the brain to muscles/tissues.
Typically involves TWO neurons. The UPPER MOTOR NEURON begins in the cerebral cortex or brainstem and carries motor information to a LOWER MOTOR NEURON in the brainstem or spinal cord which carries the info to a target muscle or tissue.
Where do the UPPER MOTOR NEURONS of the DESCENDING TRACTS originate?
The PRECENTRAL GYRUS
Describe Decussation
Some spinal tracts crossover the brain/body as they travel to and from the brain. This is responsible for phenomenon of one side of the brain processing sensory and motor information for the opposite side of the body. A lot of this occurs in the brainstem.
WIth regards to spinal tracts what does BILATERAL mean?
There is one on each side of the spinal cord.
What does IPSILATERAL mean with regards to tracts?
They originate and terminate on the SAME SIDE of the body/brain.
What does CONTRALATERAL mean with regards to tracts?
They decussate, they cross over from one side of the body to the other.
What is a nerve?
A bundle of neuronal axons covered in connective tissues.
What is an individual nerve fiber surrounded by?
ENDONEURIUM
Individual nerve fibers are bundled together into fascicles by what?
PERINEURIUM
Nerve fiber fascicles are bundled together into a nerve by what?
EPINEURIUM
What does it mean to say a nerve is MIXED?
A MIXED NERVE contains Motor and Sensory neurons and Myelinated and Unmyelinated neurons.
To say a nerve is a MOTOR Nerve means what?
It ONLY carries motor nerve fibers.
To say a nerve is a SENSORY nerve means what?
It ONLY carries sensory nerve fibers. These are VERY uncommon, best examples are the Optic and Olfactory nerves.
What are GANGLIA?
Swellings along a nerve where there is a concentration of synapses between axons of presynaptic neurons and dendrites and neuronal cell bodies (soma) of postsynaptic neuron.
Dorsal roots carry what? where?
They carry SENSORY information back to the CNS.
Ventral roots carry what? where?
They carry MOTOR information away from the CNS.
After leaving the intervertebral foramen the spinal nerve divides into what?
The Dorsal, Ventral and Communicating Rami
How long is a true spinal nerve?
About an inch.
What kind of nerves are RAMI?
Mixed nerves.
Describe the Dorsal Rami
They innervate local muscles and joints of the spine and also the skin of the back.
Describe Ventral Rami
They innervate ventral and lateral skin, muscles of the trunk and also will give rise to nerves of the limbs.
Describe Communicating Rami
Allows for the flow of nerve fibers to/from the CNS and sympathetic chain (which is part of the Autonomic Nervous system.)
What are the three classes of neurons?
Sensory, Interneurons and Motor Neurons
Describe Sensory Neurons
They are specialized neurons that are capable of detecting touch, pressure, heat, light, ect…
They originate in the skin, muscles, organs and end in the CNS.
They bring information to the CNS.
Describe Interneurons
They are located exclusively in the CNS.
They are the link “between” sensory and motor neurons.
They carry out the processing of information and decision making.
Describe Motor Neurons
They are neurons that are capable of triggering an action in a muscle, gland or organ.
They start in the CNS and end at a muscle or organ.
