Podcast
Questions and Answers
What is the consequence of a few seconds of interruption in blood supply to the brain?
What is the consequence of a few seconds of interruption in blood supply to the brain?
Which artery supplies blood to the brain from the heart?
Which artery supplies blood to the brain from the heart?
How does glucose transport into the brain occur?
How does glucose transport into the brain occur?
What critical function do astrocytes perform in the blood-brain barrier?
What critical function do astrocytes perform in the blood-brain barrier?
Signup and view all the answers
What percentage of total blood supply does the brain receive?
What percentage of total blood supply does the brain receive?
Signup and view all the answers
What is the primary role of the blood-brain barrier?
What is the primary role of the blood-brain barrier?
Signup and view all the answers
Which sensory process involves awareness of sensory stimulation?
Which sensory process involves awareness of sensory stimulation?
Signup and view all the answers
What can result from a few minutes of interrupted blood supply to the brain?
What can result from a few minutes of interrupted blood supply to the brain?
Signup and view all the answers
What is the primary role of cerebrospinal fluid (CSF) in the central nervous system (CNS)?
What is the primary role of cerebrospinal fluid (CSF) in the central nervous system (CNS)?
Signup and view all the answers
Which structures are primarily affected by increased intracranial pressure?
Which structures are primarily affected by increased intracranial pressure?
Signup and view all the answers
Which structures are involved in the circulation of cerebrospinal fluid (CSF)?
Which structures are involved in the circulation of cerebrospinal fluid (CSF)?
Signup and view all the answers
What structure forms the central nervous system (CNS) during development?
What structure forms the central nervous system (CNS) during development?
Signup and view all the answers
How does cerebrospinal fluid (CSF) achieve circulation within the CNS?
How does cerebrospinal fluid (CSF) achieve circulation within the CNS?
Signup and view all the answers
What is the primary function of the choroid plexus in the brain?
What is the primary function of the choroid plexus in the brain?
Signup and view all the answers
What condition is characterized by an accumulation of cerebrospinal fluid in the ventricles of the brain?
What condition is characterized by an accumulation of cerebrospinal fluid in the ventricles of the brain?
Signup and view all the answers
Which of the following statements about the composition of cerebrospinal fluid (CSF) is correct?
Which of the following statements about the composition of cerebrospinal fluid (CSF) is correct?
Signup and view all the answers
At what embryonic stage does the neural plate start to develop?
At what embryonic stage does the neural plate start to develop?
Signup and view all the answers
Which part of the brain is primarily associated with the medulla?
Which part of the brain is primarily associated with the medulla?
Signup and view all the answers
Which membrane of the central nervous system is closest to the brain tissue?
Which membrane of the central nervous system is closest to the brain tissue?
Signup and view all the answers
Which of the following structures develop from the neural crest?
Which of the following structures develop from the neural crest?
Signup and view all the answers
What is the primary source of fuel metabolized by the brain?
What is the primary source of fuel metabolized by the brain?
Signup and view all the answers
How much cerebral spinal fluid (CSF) is contained in the ventricles?
How much cerebral spinal fluid (CSF) is contained in the ventricles?
Signup and view all the answers
Which pathway constitutes the return of cerebrospinal fluid (CSF) to the bloodstream?
Which pathway constitutes the return of cerebrospinal fluid (CSF) to the bloodstream?
Signup and view all the answers
What pushes the brain out of the base of the skull in cases of brain edema?
What pushes the brain out of the base of the skull in cases of brain edema?
Signup and view all the answers
Study Notes
Nervous System Divisions
- Afferent (sensory input): Cell bodies outside the central nervous system (CNS)
- Cranial nerves (somatic, visual, olfactory, taste, auditory, vestibular)
- Spinal nerves (somatic sensation: touch, temperature, pain; visceral)
- Efferent (motor output): Cell bodies inside the CNS
- Cranial nerves
- Spinal nerves
- Somatic efferent: Innervates skeletal muscle; only excitatory (acetylcholine - ACh)
- Autonomic efferent: Innervates interneurons, smooth & cardiac muscle; excitatory and inhibitory
- Enteric
Brain Anatomy
- Cerebrum (cortex): Includes frontal, parietal, temporal, and occipital lobes; also corpus callosum, and thalamus.
- Brainstem: Composed of midbrain, pons, and medulla.
- Cerebellum: Located at the back of the brain
- Gyrus: A ridge on the surface of the brain
- Sulcus: A groove or furrow on the surface of the brain
- Spinal cord
- Ventricles: Cavities filled with cerebral spinal fluid (CSF)
- Gray matter: Areas containing cell bodies of neurons
- White matter: Areas containing mostly axons of neurons, myelinated and unmyelinated
- Basal nuclei (ganglia): Clusters of neurons within the brain
- Limbic system: Parts of the brain involved in emotions
Spinal Cord Divisions
- Cervical nerves (8 pairs): Neck, shoulders, arms, and hands
- Thoracic nerves (12 pairs): Shoulders, chest, upper abdominal wall
- Lumbar nerves (5 pairs): Lower abdominal wall, hips, and legs
- Sacral nerves (5 pairs): Genitals and lower digestive tract.
- Coccygeal nerves (1 pair):
Spinal Cord Anatomy
- Dorsal horn
- Gray matter
- Ventral horn
- Spinal segment
- Spinal nerve
- Central Canal
- White matter
- Dorsal root
- Ventral root
- Dorsal root ganglion
Cranial Nerves
- Twelve pairs of nerves that emerge directly from the brain
Brain Edema
- Increased intracranial pressure pushes the brain out of the skull base
- May compress the brainstem and cranial nerves, affecting things like pupillary responses
Early Development of the Nervous System
- Blastocyst (week 1): Ball of cells with inner cell mass
- Blastocyst (week 2): Further development from blastocyst (week 1)
- Blastocyst (week 3): Still further development from prior blastocysts
- Embryonic disk
- Neural plate
- Neural tube
Development: The Neural Tube
- Ectoderm
- Mesoderm
- Embryonic disk
- Endoderm
- Neural plate
- Neural Groove
- Neural tube
- Neural crest
- PNS (peripheral nervous system): Part of PNS forms dura later.
- CNS (central nervous system): Part of CNS forms neural tube.
The Neural Tube
- Vesicles develop during week 4: Forebrain, midbrain, hindbrain
- The neural tube becomes the CNS
- Forebrain
- Midbrain
- Hindbrain
- Cerebral hemispheres
- Thalamus
- Midbrain
- Pons
- Medulla
- Cerebellum
- Spinal cord
- Cavity becomes ventricles and central canal
Cerebrospinal Fluid (CSF)
- Ventricles contain 150 ml of CSF
- Produced by the choroid plexus (mainly the two lateral ventricles) at a rate of 500 ml/day
- CSF supports and cushions the CNS; equals gravity in the brain.
- Provides nutrition to the brain
- Removes metabolic waste through absorption at arachnoid villi
- Sterile, colorless, acellular fluid containing glucose
- Circulation is passive (not pumped)
- CSF circulation includes, Foramens of Munro, Cerebral aqueduct, Central canal, and Fourth ventricle
- Hydrocephalus
- Communicating
- Noncommunicating
Meninges (membranes) of the CNS
- Meninges cover the brain and spinal cord
- Skin
- Bone
- Subarachnoid space
- Dura mater
- Arachnoid membrane
- Pia mater
- Trabeculae
- Blood vessels
Dural (venous) sinus
- CSF returns to the blood at the dural sinus
- Arachnoid villi
Blood Supply to the Brain
- Glucose is the brain's only metabolized substrate; little glycogen.
- Brain needs continuous glucose and oxygen supply (no insulin needed).
- A few seconds of interruption leads to loss of consciousness, minutes lead to neuronal death (stroke)
- Brain receives 15% of total blood but is 2% of total mass
- Internal carotid artery (base of brain)
- Vertebral artery
- Arteries (external/common carotid and aorta) feed the brain.
- Circle of Willis: Safety factor
Cerebral Circulation: CSF and Blood
- Dural sinus
- Venous system
- Brain
- Circle of Willis
- Basilar artery
- Vertebral arteries
- Carotid Arteries
- Blood
- Choroid plexus
- CSF
- Subarachnoid space
- Arachnoid villi
Blood-Brain Barrier (capillary wall)
- Lipid-soluble substances easily pass
- Water (and CO2) permeable
- Prevent passage of large molecules (most plasma proteins)
- Tight junctions between endothelial cells
- Active transport of glucose, specific amino acids across
- Foot processes of astrocytes
Blood-Brain Barrier: Astrocytes (glia)
- Provide structural support
- Induce tight junctions
- Phagocytosis of debris
- Glutamate and K+
Sensory Modalities
- Sensory System, Modality, Stimulus energy, Receptor Class (table of values)
Perception of the External World
- Sensation: Awareness of sensory stimulation
- Perception: Understanding a sensation's meaning
- Law of specific nerve energies: Regardless of activation method, sensations match receptor type.
- Law of projection: Sensations are felt at receptor locations
Sensory Inputs
- Labeled-line: Brain knows modality and location of every sensory afferent.
- See corresponding laws of nerve energies and projections
Sensory Receptors
- Transduction: Stimulus energy to receptor membrane to receptor cell to CNS, with ion channel activation
- Receptor activation, adequate stimulus, specificity (adequate stimulus), transmission to CNS
Stimulus Intensity
- Magnitude of receptor potential
- Frequency of action potentials
- Magnitude of neurotransmitter release (graded responses across RF)
Adaptation of Afferent Response
- Majority of afferents have adaptation
- Non-adapting: Encodes stimulus intensity, slow changes
- Slowly adapting: Some stimulus intensity, moderate changes
- Rapidly adapting: Fast stimulus changes
Receptive Field (RF)
- Region of space that activates a sensory receptor or neuron
- Graded response across receptive fields
- The output is proportional to stimulus intensity
- Overlapping receptive fields produce a population code
Stimulus Acuity and RF Size
- Small RFs: High acuity
- Large RFs: Low acuity; lower acuity on the back versus the lips
Lateral Inhibition
- Sharpening of sensory acuity; graded responses across RF
- Contrast is emphasized across receptive fields
Descending Pathways
- Modulate sensory inputs
- Sensory information is shaped by both bottom-up and top-down mechanisms
- Presynaptic inhibition
Referred Pain
- Visceral and somatic pain afferents synapse on the same neurons in the spinal cord
- Perception of pain
- Heart attacks can refer pain to the left arm
- Locations of referred organs: Lung, diaphragm, heart, stomach, pancreas, liver & gallbladder, Small intestine, Ovaries, Appendix, Ureters, Colon, Urinary bladder, and Kidneys
- Descending pathways regulate nociceptive information: Analgesia (top down) from brain regions.
- Opiate neurotransmitters (presynaptic inhibition)
Reduction of Pain
- Descending pathways from the brainstem – Opiate neurotransmitters (e.g., morphine)
- Reduction of Pain through presynaptic inhibition
- Substance P released in spinal cord.
Visual Perception
- Visual perception is context-dependent
- Retina reports relative intensity of light
- Anatomy of the eye: Retina pigment epithelium, Optic nerve, blood vessels, Fovea centralis (highest visual acuity), Optic disk (blind spot)
- Lens refracts light to a single point
- Cornea refracts light more than lenses; focuses light for clear vision
- Accommodation for near vision: Ciliary muscles control lens shape. (Limited focal range)
- Common optical defects
- Nearsighted (myopic): Eyeball too long; corrected with concave lenses
- Farsighted (hyperopic): Eyeball too short; corrected with convex lenses
- Astigmatism: Cornea or lens is not spherical; corrected with specialized lenses
- Presbyopia: Stiff lens, cannot accommodate for near vision; corrected with reading glasses or bifocals
- Cataracts: Changes in lens color
Organization of the retina
- In fovea centralis, the retinal circuitry is shifted out of the way
- Rods, cones, bipolar cells, horizontal cells, amacrine cells, and ganglion cells (transduction, processing, and convergence)
Phototransduction
- Light activates opsin molecules (rhodopsin in rods)
- Cascade of events (G protein, second messenger, enzyme, ion channels) which causes hyperpolarization
Differences between rods and cones
- Rods: High sensitivity, night vision, more rhodopsin, high amplification, slow response time, sensitive to scattered light, low acuity, not present in fovea centralis, achromatic, one type of opsin
- Cones: Low sensitivity, day vision, less opsin, lower amplification, faster response time, most sensitive to direct light, high acuity, concentrated in central fovea, chromatic, three types of opsin
Light and Dark Adaptation
- Dark adaptation: Rods "re-activate", cones take over
- Light adaptation: Rods initially saturated, become inactive, cones take over
Light and Dark Adaptation (processes)
- Phototransduction: Opsin (protein) with retinene (related chromophore to vitamin A)
Retina Reports Relative Intensity of Light
- Light-dependent signaling
Organization of the retina (again?)
- Bipolar cells, horizontal cells, amacrine cells
- Rods, cones, Ganglion cells
Retinal ganglion cells
- Center-surround receptive fields: Contrast across receptive fields
- Uniform light
Photoreceptors
- Chromatic sensitivity; Different opsin molecules determine chromatic sensitivities
- Rods and cones
Color Perception
- Color perception is context-dependent
Retinal ganglion cells
- Color-opponent receptive fields: The output encodes brightness and color
Color Blindness
- Different gene mutations can prevent the activation of retinal receptors
Flow of Visual Information in the Brain
- Optic nerve
- Optic tract
- Optic chiasm
- Lateral geniculate nucleus (LGN)
- Optic radiations
- Visual cortex in occipital lobe
The Anatomy of Visual Field Deficits
- Loss of vision in ipsilateral eye, contralateral visual field, bilateral loss of temporal visual hemifields
Cortical Representation of the Visual World
- Polymodal: Vision and other sensory modalities combined
- Parietal visual stream (where): Large receptive fields (RFs), spatial features and motion
- Primary visual corte (what): Small receptive fields (RFs), lines, segments
V1 Orientation Elective Responses
- Retina
- LGN (center-surround responses)
- Primary visual cortex
The Pupillary reflex
- Light in one eye: Both pupils constrict
- 3rd cranial nerve involved and midbrain functions.
Auditory System:
-
Amplitude and frequency of sound
- Hertz (cycles per second)= frequency=pitch
- Amplitude= loudness
- Normal audibility curve
- Anatomy of the ear: Pinna, External auditory canal, Middle ear (malleus, incus, stapes), Inner ear (cochlea), Eustachian tube, Tympanic membrane
- Anatomy of the inner ear: Semicircular canals, oval window, round window, Utricle (Horz), Saccule (Vert), Sensory epithelia, cochlea
- Flow of sound energy: amplification (modulated skeletal muscles), fluids in cochlea, round window, and oval window
- Motion of basilar membrane is frequency dependent: Local vibrations dependent on sound frequency
- The basilar membrane in action: Cochlea response to sound
- Cochlear duct: Organ of Corti and basilar membrane
- Deflection of basilar membrane: Shearing of hair cells, stereo cilia.
- Cochlear Amplifier: Outer hair cell "electromotility", shorten when depolarized, lengthen when hyperpolarized
- Clinical implications of outer hair cell “electromotility”: Otoacoustic emissions (reflex) used in newborns for hearing evaluation.
- Hair Cells: Contain mechanoreceptors
- Movement of hair cell stereo cilia: Sound transduction
- Tip links: Connects stereo cilia, gates ion channels
- Mechano transduction: At tip links activates afferent neurons
- Clinical implications: Ringing in ears (Tinnitus) (transient < 24 hours due to loud noises, chronic - many causes, and mostly loud noises).
Visual vs. Auditory Transduction
- Visual: High-energy photons, hard to catch, trillions of opsin molecules, slow (G-protein cascade), amplification
- Auditory: Lower energy sound waves, several hundred thousand tip links, fast (direct channel activation) no amplification
Cochlear Implants
- Implanted through round window, Electrode in scala tympani, Electrodes spaced along spiral, stimulate afferent fibers (respond to frequencies), ~12 electrodes
- Auditory nerve, spiral ganglion cell, scala vestibuli, Reissner's membrane, Organ of Corti, scala tympani, plastic transmitters, skin, and sound processors, receiving antennas, mastoid bone receiver circuitry
Central Auditory Pathways
- Primary auditory cortex, 8th cranial nerve (vestibular and auditory), thalamus, midbrain, and medulla
Vestibular Organs
- Semicircular canals: Angular acceleration
- Utricle: Horizontal linear acceleration
- Saccule: Vertical linear acceleration
- Vestibular ocular reflex: Eyes rotate in opposite direction of head rotation
Taste (Gustation)
- Papillae
- Taste cells
- Taste buds
- Taste pores
- About 10,000 taste buds
Taste Transduction
- Umami: Glutamate receptors, G-protein cascade
- Salty: Na+ channels
- Sour: H+ channels
- Bitter: Block channels
- Sweet: G-protein cascade
Central Taste Pathways
- Ipsilateral gustatory cortex
- Cranial nerves, medulla, thalamus
Olfaction
- Nasal cavity
- Olfactory tract
- Olfactory bulb
- Olfactory receptor cells
- Olfactory epithelium
- Mucus
- Cilia
Olfactory Signal Transduction
- Odorant binding
- G-protein activation
- Opening of ion channels
- About 1000 different odorant receptors
Central Olfactory Pathways
- Olfactory bulb
- Limbic system
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the functions and anatomy of the central nervous system, including the blood-brain barrier, cerebrospinal fluid, and the effects of interrupted blood supply to the brain. This quiz covers key aspects that are critical for understanding CNS physiology and its protective mechanisms.
