neuroanatomy1 Flashcards
the places in the brain where the dura matter layers are seperated?
-dural venous sinuses: important for venous drainage from the brain
- superior Sagittal sinus
-transverse sinus
-sigmoid sinus
-straight sinus
confluence of sinuses: the previous sinuses meet
what are the important structures?
-Skull
-Epidural space: contains fat, veins, spinal arteries, and lymphatics
-dura matter
-subdural space
-arachnoid matter
-subarachnoid space
-Arachnoid granulations: drainage of cerebrospinal fluid (CSF) into the venous sinuses
-falx cerebi: a sickle-shaped structure formed from the invagination of the dura mater into the longitudinal fissure between the cerebral hemispheres.
-tentorium ce·re·bel·li -ˌser-ə-ˈbe-ˌlī : an arched fold of dura mater that covers the upper surface of the cerebellum
what are the meninges of the brain?
-dura matter: periostal layer, meningeal layer, fibrous connective tissue
-arachnoid: thin , avascular
-pia matter: thin, mesodermal origin, resembling endothelium
what are the major formina?
-The foramen magnum: connecting the brain with the spinal cord
-foramen ovale: transmits the mandibular nerve, a branch of the trigeminal nerve.
-Foramen spinosum: gives passage to the middle meningeal artery and vein
-The jugular foramen: a conduit for glossopharyngeal, vagus, and accessory nerves
-External auditory canal, passageway that leads from the outside of the head to each ear
-carotid canal
what are the cranial fossae within the base of the skull
-Anterior cranial fossa: front part
lesser wing of the sphenoid bone
-midlle cranial: pituitary gland
the petrous part of the temporal bone
-posterior cranial: the cerebellum and brain stem
the occipital bone
sinuses of the brain?
- superior Sagittal sinus
-transverse sinus
-sigmoid sinus
internal jugular vein
what are the ventricles of the brain?
-2 lateral ventricles in in each cerebral hemisphere
interventricular foramens (or foramina of Monro)
-third ventricle in the diencephalon
the cerebral aqueduct
-the fourth ventricle in the hindbrain: draining directly into the central canal of the spinal cord through
Explain the cerebrospinal fluid circulation?
-CSF produced by the choroid plexus flows from the lateral ventricles in each hemispheres to the third ventricle through the foramen of Monro, into the the fourth ventricle through the sylvian aqueduct. through the foramina of luschka and magendie(median aperture) , into the subarachnoid space, up to the arachnoid granulations to be reabsorbed into the blood stream.
What is the mechanism of blood-brain barrier?
- in the sytemic capillaries lying outside the CNS, they fenstrated allowing the passage of water and solutes.
-in the CNS, the brain cappillaries have a tight juctions between the endothelial cells forming the blood brain barrier, Cellular transport is required for the passage of water and solutes between the blood and te brain
what is the mechanism of blood-CSF barrier?
-The choroid plexus capillary allows for the passage of the water and solutes, but the choroid plexus epithelial cells forms the blood-CSF barrier
-the subarachnoid villus cells carries out the CSF in one way from the subrachnoid space to the venous sinuses via giant vacuoles
What are the circumvetricles organs?
-blood barrier is interrupted
-pineal gland: secretes melatonin into the systemic circulation
-area postrema: detects toxins in the blood and acts as a vomit-inducing center
-neurohypophysis: part of hypothalamus secreting vasoprisin and oxytoxin
- The median eminence at the base of the hypothalamus releases hypothalamic-releasing hormones into the portal capillary bed for transport to the anterior pituitary
- subcommissural gland: the reabsorption and circulation of the cerebrospinal fluid
what is cauda equina?
The collection of nerves at the end of the spinal cord
Where the spinal cord ends?
the intervertebral disc between the first and second lumbar vertebrae as a tapered structure called the conus medullaris,
what is the segementation of the spinal cord?
-gray matter: centrally located and consists of cell bodies of neurons
* Dorsal Horn: contains sensory
neurons.
*Ventral Horn: contains motor
neurons.
-White matter: surrounds the gray matter and consists of myelinated axons.
*Lateral Column: a mix of sensory
and motor pathways.
*Ventral Column: motor pathways.
*Dorsal Root: bundles of sensory
nerve fibers
what are the spinal nerve segmentation?
- Dorsal Root: they carry sensory information from the body to the spinal cord.
Ventral Root: they carry motor commands from the spinal cord to the muscles and glands.
Dorsal Root Ganglion: contains cell bodies of sensory neurons. These neurons receive sensory input from peripheral receptors.
Sympathetic Ganglion: These are clusters of nerve cell bodies outside the spinal cord that are part of the sympathetic nervous system, which controls the body’s “fight or flight” responses.
explain how the inputs enter the spinal cord from the peripheral receptors?
In the sensory pathway, the process begins with peripheral receptors (e.g., mechanoreceptors) detecting stimuli. These receptors generate electrical signals. Mechanosensory afferent fibers, which are specialized sensory neurons, transmit these signals towards the spinal cord. The signals travel through dorsal root ganglion cells, clusters of cell bodies located just outside the spinal cord, which help relay the sensory information to the spinal cord. Once in the spinal cord, the signals can be further processed and relayed to the brain, allowing us to perceive and respond to the sensory information.
what is the transduction in a mechanosensor afferent?
Transduction in a mechanosensory afferent is the process by which mechanical stimuli, like touch or pressure, are converted into electrical signals in sensory neurons. Special receptors in the mechanosensory afferent detect the mechanical forces and generate electrical impulses that convey information to the nervous system. When a mechanical force, like pressure or stretching, is applied to these receptors, they undergo a physical change. This change results in the opening or closing of ion channels, allowing ions to flow in or out of the neuron. This movement of ions generates an electrical signal or action potential, which is then transmitted along the sensory neuron to convey the information to the central nervous system
what are the types of axons according to the velocity?
-Axons type A: largest and fastest, they are often myelinated
alpha: the fastest
Beta: moderate
delta: the slowest
-Axons type B: medium-sized, moderate conduction velocity
-Axons type C: the slowest conducting axons in the nervous system. They have small diameters and are typically unmyelinated.
what are the types of receptors of the skin?
-Free Nerve Endings: found in the dermis around the base of hair follicles and close to epidermis, detect temperature, pain, pressure
-Meissner’s Corpuscles: found in the dermal papillae, they do play a role in movement detection, grip control
-Merkel Cell-Neurite Complex: are located in the epidermis, They play a role in texture and shape perception
-Ruffini Endings: they are found the dermis, play a role in recognize tangential force, hand shape, motion direction
- Pacinian Corpuscles: located in the deeper layers of the skin. play a role in the perception of distant events through transmited vibrations: tool use.
what is adaptation?
-Rapid Adaptation (Phasic Receptors): Rapidly adapting mechanoreceptors respond strongly to the onset of a mechanical stimulus but quickly decrease their firing rate and become less responsive to sustained pressure, provide information about dynamic qualities of a stimulus.
-Slow Adaptation (Tonic Receptors): Slowly adapting mechanoreceptors maintain their response over the duration of a sustained stimulus. They continue to signal the presence of the stimulus as long as it persists. provide information about static qualities of a stimulus.
what are the receptors of the muscle?
- Muscle spindles are stretch receptors alert the brain that nearby joints and soft tissues are in danger of being stretched too far. They consist of intrafusal muscle fibers and a connective tissue capsule.
-Golgi tendon organs consist of thin collagen fibers that are connected in series with muscle fibers. These collagen fibers are enclosed in a capsule. they are locatted in the tendon, When the GTO is activated during contraction, it causes inhibition of the contraction (autogenic inhibition), which is an automatic reflex. When the GTO is activated during stretching, it inhibits muscle spindle activity within the working muscle (agonist) so a deeper stretch can be achieved.
what are the dermatome and myotome notions?
- dermatome: specific area of skin that is primarily supplied by a single spinal nerve or a specific segment of the spinal cord. except C1
- myotome: each spinal nerve supplies a particular set of muscles in a segment of the body.
dermatome vs peripheral innervation ?
dermatomes are a subset of peripheral nerve innervation, focusing specifically on the sensory distribution on the skin’s surface. Peripheral nerve innervation covers a wider range of functions in the peripheral nervous system, including both sensory and motor functions
What is a cauda equina?
the roots of the spinal nerves that extend beyond the termination of the spinal cord at the first lumbar vertebra in the form of a bundle of filaments within the spinal canal resembling a horse’s tail.
what is the Regulatory circuit for muscle length?
Alpha motor neurons stimulate extrafusal muscle fibers to contract, while gamma motor neurons regulate the sensitivity of the muscle spindle. The muscle spindle, with the help of Ia afferent fibers, provides information about muscle length and changes in length, allowing for reflexive adjustments in muscle tension. Renshaw receives inputs from Ia fibers so it can modulate the activity of alpha motor neurons to ensure precise control of muscle contraction.
what is regulatory circuit for muscle tension?
Alpha motor neurons (Alpha fibers): Stimulate extrafusal muscle fibers to contract, while Gamma motor neurons Regulate the sensitivity of the muscle spindle, Ib fibers (Golgi tendon organs): Detect changes in muscle tension or force.
what is a monosynaptic reflex?
- activates the agonist muscle, the muscle that produces the desired movement.
- sensory receptor (e.g., a muscle spindle) detects a stimulus (e.g., muscle stretch), a sensory neuron carries the signal to the spinal cord(anterior horn), where it directly synapses with motor neuron that stimulates the agonist muscle to contract to grnerate the desired movement
what is a polysynaptic inhibition?
- inhibit the antagonist muscle, the muscle that opposes the desired movement.
- multiple synapses
-interneurons receive sensory input and relay signals to motor neurons responsible for antagonist muscle.
-The inhibitory interneurons release neurotransmitters that inhibit the activity of the motor neurons controlling the antagonist muscle, preventing it from contracting
what is the flexor reflex?
- classic example of a polysynaptic reflex in the spinal cord
- The reflex is initiated by a noxious stimulus, such as a sharp object pricking the skin( nociceptor)
- sensory neurons transmit the information from the nociceptors to the spinal cord
- sensory neurons enter through the dorsal root and synapses with interneurons within the posterior horn of the gray matter
- nterneurons process the sensory information and relay it to various motor neurons that control muscles.
- the polysynaptic connections activates the flexor muscles, and also inhibit the antagonist muscles
