ANAT Block theory #2 Flashcards
What are the three steps of the nervous system?
- Sensory input
- Integration
- Motor output
What is sensory input?
Sensory input from the environment is detected by sensory nerves and travels through the body to communicate with other nerve cells
What is integration?
Processing and interpretation of sensory input
What is motor output?
a response to integrated stimuli; the response activates muscles or glands by sending motor output through motor nerves
What are the two principal subdivisions of the nervous system?
Central
Peripheral
What is the function of the CNS?
»Where all signals come to and from
»Where they are integrated
»Where information can be stored
What is the function of the PNS?
System that brings those signals to and from the CNS
What are the two divisions that the PNS can be further broken down into?
Sensory (afferent) division
Motor (efferent) division
What does the sensory division do?
Relays information to CNS
Sensing things such as sight, smell, touch and even pain
Sends the information to the CNS through sensory neurons
What does the motor division do?
Relays information from CNS to target cells
The actual response that is elicited
Signal comes from the CNS, the brain, or spinal cord and is relayed to a target cell through efferent neurons
What subdivisions can the motor (efferent) division be further divided into?
Somatic
Autonomic
What is the function of the somatic nervous system? And how does it do that?
Controls voluntary movement
Signal comes from the CNS through the efferent neurons to a target skeletal muscle cell, eliciting movement of that muscle
What is the function of the autonomic nervous system?
Controls involuntary movement
What can the autonomic nervous system be further divided into?
Sympathetic - fight or flight
Parasympathetic - rest and digest
What do neurons do?
Structural units of the nervous system.
Allow for communication within and between the CNS and PNS.
Can generate and transmit rapid electrical signals to other neurons
Neuron Structure
cell body, dendrites, axon
What does the cell body do in a neuron?
Functions to transfer electrical signals from the dendrites to the axon
Also called the ‘soma’
Houses the nucleus and other organelles
What does the dendrites do in a neuron?
Receive the neuronal signal form other neurons and transfer those signals to the cell body
What does the axon do in a neuron?
Carry the signal from the cell body to the axon terminals, where the signal is then transferred to other neurons or organs
What is the direction of a nerve impulse?
Unidirectional
What are the characteristics of a pseudo-unipolar neuron?
Have one cellular process that splits into a dendrite and an axon.
Example: general sensory nerves
What are the characteristics of a bipolar neuron?
Have one dendrite and one axon that extend directly from the cell body
Have two distinct cellular processes
Only found in special sense, like sight and hearing
What are the characteristics of a multipolar neuron?
Have multiple dendrites and one axon, summing to three or more cellular processes
Number of dendrites is variable
Most common type of neurons
Example: motor neurons
What is the function of glia?
- Function to protect and support neurons and aid in sending signals between neurons to improve communication
- These cells DO NOT generate or transmit nerve impulses
What are the 4 supporting cells of the CNS?
- Astrocytes
- Microglia
- Ependymal
- Oligodendrocytes
What is an astrocyte?
- Large star shaped cells with numerous processes
- Communicate with neurons and blood vessels to maintain the integrity of the neural tissue
- Most abundant
What is microglia?
-Perform many protective functions in the CNS
-Able to phagocytose, or engulf and destroy pathogens, and eliminate waste products from other cells
-Least common
What is ependymal?
-Cuboidal in shape
-Line cavities of brain and spinal cord
-Assist in the production, circulation, and monitoring of cerebrospinal fluid (CSF)
What are oliogodendrocytes?
Wrap around axons in the CNS to form myelin sheath
What is myelination?
-An important function of neuroglia is to myelinate parts of an axon
-Myelin is composed mainly of fat
-Appears white
-Insulates the axon and increases the speed at which electrical signals can travel down the axon
What are unmyelinated axons called?
Nodes of Ranvier
What is the main type of neuroglial cell in the PNS called?
The Schwann Cell
What is a Schwann cell?
They wrap the axon with myelin sheath. These are found in the PNS and only myelinate one axon at a time.
What parts is the brain composed of?
Cerebrum
Brainstem
Cerebellum
What makes up the bulk of the brain?
Cerebrum
What is the telencephalon?
A part of the cerebrum
What are the features of the Telencephalon?
Cerebral hemisphere
Cerebral cortex
Sulci and gyri
What is the cerebral hemisphere?
-Cerebrum is made up of two paired hemispheres: the right and the left cerebral hemisphere
-Hemispheres are separated by the longitudinal fissure
What is the cerebral cortex?
outer layer of the cerebrum - can be distinguished by its dark, grey colour
What are the sulci and gyri?
-Folds in the cerebrum
-Increases surface area of neural tissue which increase the functional capacity of the tissue
-Fissures and grooves: sulci
-Lumps and bumps: gyri
Where is the pre-central sulcus?
running in front of and parallel to the central sulcus, separated from it by the precentral gyrus.
Where is the lateral sulcus?
between temporal and parietal/frontal lobes
Where is the parieto-occipital sulcus?
between parietal and occipital lobes
Where is the post-central sulcus?
parallel to, and behind, the central sulcus in the human brain.
Where is the central sulcus?
between frontal and parietal lobes - it also separates the motor from the sensory cortex
What does the pre-central gyrus do?
Responsible for sending motor output signals. It is located anteriorly to the central sulcus
What does the post-central gyrus do?
Responsible for sending motor output signals. It is located anteriorly to the central sulcus
What does the post-central gyrus do?
Responsible for receiving sensory input related to touch and feel. It is located posteriorly to the central sulcus
What are the four lobes?
frontal, parietal, temporal, occipital
Grey Matter of the brain
-Consists of nerve cell bodies, short interneurons, and glial cells
-Contains the central canal which is filled with CSF
-Each half of the grey matter is divided into regions called horns
-Can be found in cerebral cortex and inner areas of the brain
What does the ventral horn do?
carries motor information
What does the dorsal horn do?
carries sensory information
White matter of the brain
-Lines the outside of the grey matter of the spinal cord (but is on the inside of the brain)
-Consists of bundles of nerve fibres or axons
-Consists of tracts of fibres separated into anterior, lateral, and posterior funiculi (bundles)
-Each bundle is connected to a specific region of the brain
What are the three categories of white matter tracts?
- Association
- Commissural
- Projection Fibres`
What does the association fibres do?
Facilitate communication within ONE hemisphere
What does the commissural fibres do?
facilitate communication between two hemispheres
e.g. corpus callosum
What does the projection fibres do?
Facilitate communication between different levels of the CNS
E.g. between brain and spinal cord
What are the components of the Diencephalon of the cerebrum?
-Thalamus
-Hypothalamus
What is the thalamus?
»Deep brain structure with two bodies (one per hemisphere)
»Responsible for relaying sensory information (except the sense of smell) to other areas of the brain
What is the hypothalamus?
»Small structure below the thalamus
»Connected to pituitary gland
»Controls the release of hormones through the pituitary gland
What is the brainstem?
Area of the brain that connects the brain to the spinal cord
Situated just below the diencephalon
What is the brainstem comprised of?
comprised of?
midbrain, pons, medulla
What is the midbrain?
*Most superior aspect of the brainstem
*Anteriorly, the midbrain consists of large white matter tracts that make up the cerebral peduncles
*Postero-lateral view: midbrain has two pairs of raised bumps, known as the superior and inferior colliculi
What is the pons?
*Structure in the middle of the brainstem
*Located anterior to the 4th ventricle and the cerebellum
*Pons has fibers connecting it to the cerebellum, allowing for communication between these two structures
What is the medulla oblongata?
*Most inferior structure
*Continuous with the spinal cord
Where is the cerebellum located?
Structure that is appended to the back of the brainstem
Sits underneath the occipital lobe of the cerebrum
What does the cerebellum do?
coordinates movement and balance
What are meninges?
dura mater, arachnoid mater, pia mater
What do the meninges do?
They serve as a protective covering of the CNS
What is the dura mater?
Dura Mater is the most superficial and tough of the meninges. It is composed of a double layer of connective tissue that attaches firmly to the skull
What is the arachnoid mater?
*Loosely covers the brain
*Creates an area called the subarachnoid space
*This space is filled with cerebrospinal fluid (a protective fluid) and blood vessels
What is the pia mater?
This is the internal layer that attaches to the cerebral cortex
What do the ventricles do?
Support and protection to the brain
What are the ventricles in the brain made up of?
»Made up of four hollow spaces that are continuous with each other and the spinal cord
»Spaces contained cerebrospinal fluid (CSF
Lateral ventricles
*Lateral ventricles are paired “c” shaped spaces deep within the cerebral hemisphere
*Portion of the lateral ventricles can be found in each lobe
Third ventricle
-The singular third ventricle is located in the middle of the diencephalon between the two halves of the thalamus.
-Connected to the lateral ventricles by the interventricular foramina (of Monro)
Fourth ventricle
-Sits between the pons/medulla and the cerebellum
-Connected to the third ventricle by the cerebral aqueduct
-Continuous with the central canal of the spinal cord and the subarachnoid space
How many ventricles are in the brain?
- Lateral ventricles (2)
- Fourth ventricle (1)
- Third ventricle (1)
*All together 4
What is the directional flow of CSF?
- Lateral Ventricles
- Interventricular Foramen
- Third ventricle
- Cerebral Aqueduct
- Fourth Ventricle
- Subarachnoid space
Where is the spinal cord located?
vertebral canal and is supported by the vertebral column
What is the purpose of the spinal cord?
Facilitates communication between the central nervous system and peripheral nervous system through the spinal nerves
Where does the spinal cord begin?
foramen magnum
Where does the spinal cord end?
L2
What happens below the L2 level?
Inferior to L2, the axons emerging from the spinal cord are known as the cauda equina
Within the cauda equina, the filum terminale (a small thin strand of pia mater) anchors the spinal cord to the sacrum
Order of spinal cord regions from top to bottom
Cervical, thoracic, lumbar sacral
Why do spinal enlargements occur?
Enlargements occur because of the additional nerves exiting the spinal cord that supply the limbs
Where is the spinal cord enlarged?
cervical and lumbar regions
What does the cervical enlargement supply?
upper limbs
What does the lumbar enlargement supply?
lower limbs
When the C1 to C3 are injured what happens?
Limited movement of the head and neck only
When the C5 is injured, what happens?
Head, neck, and shoulder movement, bend elbows and rotate hands
What is injured when there is normal upper body movement, but some degree of impairment in the legs?
T1-T6 injury
Where is the grey matter of the spinal cord located?
inside
What does the grey matter in the spinal cord consist of?
Consists of a ventral horn (which carries motor information), and a dorsal horn (which carries sensory information)
Where is the white matter of the spinal cord located?
White matter lines the outside of the grey matter of the spinal cord
Where is the white matter of the spinal cord consist of?
Consists of tracts of fibers separated into anterior, lateral, and posterior funiculi (bundles)
What is grey matter in the spinal cord composed of?
Mainly composed of dendrites, neuron cell bodies, glial cells, and unmyelinated axons
What is white matter in the spinal cord composed of?
Mainly composed of myelinated axons
What does the endocrine system work at?
Homeostasis
What is homeostasis?
Proper balance of chemicals and other substances in the body and the harmonious functioning and coordination of all the various bodily processes and organ systems
What does the endocrine system do?
System helps maintain state of balance in the body by performing a regulatory role for all the other organ systems by secreting hormones and glands
What are hormones?
Chemical messengers that travel through our circulatory system to other parts of the body in order to control or regulate a body process
Define endocrine
Cells of these glands secrete hormones directly into the interstitial fluid surrounding the secretory cells. The hormones are then picked up by the blood capillaries
Glands secrete their hormones within the gland
Define exocrine
Glands that secrete cell products into a duct system
Glands that secrete their hormones outside the gland
pituitary gland
-base of the brain that extends from the hypothalamus
-known as the “master gland”
-produces and releases hormones that control all other endocrine glands
thyroid gland
-produces thyroid glands important for homeostasis
-sits anterior to the trachea
-calcium homeostasis
parathyroid glands
-four small oval glands situated on the back of thyroid gland
-paired (2 superior, and 2 inferior)
-maintenance of calcium homeostasis
pancreas
Produces enzymes for digestion and the hormone insulin that regulates blood sugar levels
adrenal glands
-sit on top of each kidney
-“suprarenal glands”
-production of corticosteroids
-maintenance of fluid balance
Where is the pituitary gland located?
Located inferior to the hypothalamus
Sits in a concavity of the sphenoid bone in the middle of the skull
Physical contact between the hypothalamus and the pituitary gland allow for…
allows for communication between the nervous and endocrine system
What are the two lobes that the pituitary gland are divided into?
Anterior (Adenohypophysis)
Posterior (Neurohypophysis)
What hormones are in the anterior lobe of the pituitary gland?
-Thyroid stimulating hormone (TSH)
-Prolactin (PRL)
-Adrenocorticotropic Hormone (ACTH)
-Growth hormone (GH)
-Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
-Melanocyte Stimulating Hormone (MSH)
What hormones are in the posterior lobe of the pituitary gland?
Oxytocin
Antidiuretic Hormone (ADH)
What does the thyroid stimulating hormone do?
Acts on the thyroid gland, causing it to release thyroid hormones
What does prolactin do?
Induces the mammary glands of the breast to produce milk
What does Adrenocorticotropic Hormone do?
regulate the glucocorticoid (steroid) hormone cortisol.
What does the growth hormone do?
stimulates growth in cells
What does the Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) do?
Both act on the gonads
They stimulate secretion of estrogen and progesterone, and maturation of oocytes in the ovaries
They stimulate secretion of testosterone and sperm production in the testes
What does melanocyte do?
stimulates melanocytes in the skin to produce pigment
Where does neurohypophysis get its name?
Known as neurohypophysis because it is made up of nervous tissue
What does ADH do?
The general function of ADH is to promote reabsorption of water at the kidneys
What does oxytocin do?
The function of oxytocin is to promote uterine contractions during childbirth. It also plays a role in breastfeeding
What stains darker, the anterior lobe of the pituitary gland or the posterior?
The anterior
What is the anterior lobe of the pituitary gland made up of?
-Glandular tissue
-Made up of glandular acini (small sac-like cavities) that are arranged in small groups that are surrounded by connective tissue
What is the posterior lobe of the pituitary gland made up of?
-Composed of nervous and connective tissue
-Does not contain acini
What is an important structure in maintaining metabolic homeostasis?
The thyroid gland
Where does the thyroid gland lie?
Sits in the neck anterior to the trachea and inferior to the larynx
What is the thyroid gland composed of?
Follicles that are lined with simple cuboidal follicular cells.
These surround a central lumen called colloid.
Between the follicles are parafollicular (“C”) cells
What do the follicular cells in the thyroid gland produce?
Triiodothyronine (T3) and Thyroxine (T4)
Act to increase the rate of metabolism and oxygen consumption
What do the C cells in the thyroid gland produce?
The C cells are important in calcium homeostasis
They produce calcitonin - lowers the blood calcium concentration
What are the parathyroid glands?
four tiny glands embedded in the back of the thyroid
What do the parathyroid glands do?
What do the parathyroid glands do?
Where are the adrenal glands located?
on top of the kidneys
What structures can the adrenal glands be divided into?
-the cortex
-the medulla
What does the adrenal medulla produce?
Produces epinephrine and norepinephrine in response to sympathetic nervous system stimulation resulting in an autonomic (flight or fight) response
What are the three layers that the adrenal cortex is divided into? And what do they do?
The outer layer
The middle layer
The inner layer
Collectively they produce two dozen hormones
What does the outer layer of the adrenal cortex produce?
Mineralocorticoids
What does the middle layer of the adrenal cortex produce?
Glucocorticoids
What does the inner layer of the adrenal cortex produce?
Androgens
True or false: the pancreas is a mixed gland (has both exocrine and endocrine functions)?
True
What do beta cells do?
produce insulin and functions to lower blood glucose levels (hypoglycemic)
What do alpha cells do?
produce glucagon and functions to increase blood glucose levels (hyperglycaemic)
What does the PNS contain?
-Contains all of the nerves outside of the brain and spinal cord
-PNS contains the spinal and cranial nerves
What does the sensory (afferent) system do?
Transmits sensory information from the periphery to the CNS
What does the motor (efferent) system do?
Transmits motor commands from the CNS to the periphery
What does the somatic nervous system do?
controls voluntary movements
What does the autonomic nervous system do?
Involuntary motor control of smooth and cardiac muscle
What does the sympathetic nervous system do?
fight or flight
What does the parasympathetic system do?
rest and digest
How do cranial nerves emerge?
Emerge in pairs from the brain and brainstem instead of the spinal cord
How many pairs of cranial nerves are there?
12
Nerve I
Olfactory
Sensory only
Smell
Nerve II
Optic
Sensory only
Vision
Nerve III
Oculomotor
Motor only
Movement of the eye (there’s three)
Nerve IV
Trochlear
Motor only
Movement of the eye
Nerve V
Trigeminal
Sensory - forehead, eye, upper jaw, lower jaw
Motor - muscles of mastication
Nerve VII
Facial
Sensory - taste for anterior 2/3 of tongue
Motor - muscles of facial expression, parasympathetic innervation of tear and salivary glands
Nerve VIII
Vestibulocochlear
Sensory only
Equilibrium and hearing
Nerve IX
Glossopharyngeal
Sensory - sensory innervation of the pharynx, taste from posterior 1/3 of tongue
Motor - pharynx muscles, parasympathetic innervation of salivary glands
Nerve X
Vagus
Sensory - sensory innervation of the larynx
Motor - Pharynx and larynx muscles, parasympathetic innervation of the thoracic and abdominal organs
Nerve XI
Accessory
Motor only
Trapezius and sternocleidomastoid muscles
Nerve XII
Hypoglossal
Motor only
Muscles of the tongue
How many pairs of spinal nerves are there?
31
How is a spinal nerve formed?
A spinal nerve is formed by the union of the posterior (sensory) and anterior (motor) roots of the spinal cord
How are spinal nerves named?
Letter = refers to the region of the spinal cord
Number = refers to the level
What are the nerve plexuses?
Once the spinal nerves exit the vertebral column, fibres from the anterior roots (motor) come together and then redistribute into new networks of nerves (plexuses) that mostly innervate muscles of the limb
What do the nerve plexuses contain?
Each plexuses therefore contains fibres (a collection of axons) from a combination of spinal nerves
What is the functional importance of the nerve plexuses?
In the case of injury, the contribution of multiple spinal nerves into the nerve plexuses ensures innervation to the muscle
What nerve plexuses correspond to the cervical enlargement?
The cervical and brachial plexuses correspond to the cervical enlargement
What nerve plexuses correspond to the lumbosacral enlargement?
Lumbar and sacral plexuses correspond to the lumbosacral enlargement
What does “two neuron pathway” mean?
Between the CNS and any target organ, there are two neurons
Between the CNS and any target organ, there are two neurons
The automatic nervous system
What is the preganglionic neuron?
-has its cell body within the CNS
-The axon enters into the PNS and travels to the autonomic ganglion
What is the autonomic ganglion?
-where the preganglionic and postganglionic neurons meet and communicate
-located in the PNS
What is a postganglionic neuron?
-entirely in the PNS
-its cell body is in the autonomic ganglion, while its axon travels to the target organ
