Brain & Behavior Ch. 1

I.  The Nervous System is Made of Specialized of Cells (Neuroanatomy I PowerPoint)

--Cajal:  what is the neuron doctrine?

  1. neuron is an anatomical unit, the fundamental structural and functional unit of the nervous system

  2. neuron composed of cell body, dendrites, axon

  3. neurons are discrete cells/not continuous with other cells

  4. points of connection between neurons are called synapses

  5. neuron is a physiological unit that transmits information throughout the nervous system via electrochemical signals.

--What are the 4 functional zones of a neuron?

  • input zone: receives info through dendrites

  • integration zone: cell body (soma) integrates info it receives

  • conduction zone: single axon conducts output away from cell body

  • output zone: axon terminals transmit signals across signals

--Differentiate motor neurons, sensory neurons, interneurons

  • motor neurons: carry signals from the CNS to muscles, facilitating movement and motor control; large, long axons, synapse on muscles

  • sensory neurons: detect sensory information from the environment and transmit it to the CNS; various shapes that best respond to specific environmental stimuli (light, odor, touch, etc.)

  • interneurons: connect sensory and motor neurons within the CNS, playing a crucial role in processing information and reflex arcs; typically short with many dendrites, allowing them to integrate diverse signals

--What are the 3 general types of neurons?  (i.e. structural types)

  • multipolar: one axon, many dendrites; most common

  • unipolar: one axon that splits into two branches; primarily involved in sensory functions

  • bipolar: one axon and one dendrite; often found in special sensory organs (e.g., retina, olfactory system) 

Synapses

--What are synaptic vesicles? Neurotransmitter receptors?

  • synaptic vesicles: membrane-bound sacs within the presynaptic neuron that store neurotransmitters until they are released into the synaptic cleft during neurotransmission

  • neurotransmitter receptors: molecules situated on the postsynaptic membrane that bind to neurotransmitters released into the synaptic cleft, initiating a response in the receiving neuron

--presynaptic membrane is identifiable by synaptic vesicles; postsynaptic membrane identifiable by clusters of postsynaptic receptors   

--What is the functional significance of dendritic branching?

  • Dendritic branching increases the surface area of the neuron, allowing for a greater number of synaptic inputs and enhancing the neuron's ability to integrate signals from multiple sources

--What is a dendritic spine?  What are 2 functional purposes of dendritic spines? (i.e. what 2 things do spines contribute to the neuron?)

  • dendritic spine: a small, finger-like projection on the dendrites of neurons that serve as the primary sites for synaptic connections.

    • Functional purposes:

      • Synaptic transmission: Dendritic spines facilitate the transmission of signals between neurons by hosting synapses, which are critical for communication in the nervous system.

      • Plasticity and learning: These spines can undergo structural changes, which are believed to play a key role in synaptic plasticity, thereby contributing to learning and memory processes.

--Neuroplasticity: capacity for continual remodeling of connections b/t neurons; synapses and spines can come and go  

--Primary cilium:  single non-motile projection from most neurons

  • important for neural development and for regulation of feeding

  • human diseases called ciliopathies result from defects in primary cilia

  • a serotonergic synapse onto primary cilia has been demonstrated

 

--Axons:

--What is the axon hillock?  Axon collateral?

  • axon hillock: the conical structure at the beginning of an axon where action potentials are initiated

  • axon collateral: branches of an axon that allow a single neuron to communicate with multiple target cells

--What are the 2 main functions of an axon?

  • To transmit action potentials away from the cell body to other neurons or target organs

  • To facilitate communication between the neuron and various parts of the body by connecting to multiple synaptic terminals

--Glia: 

--What are the 4 basic classes of glia?  (be familiar with the functions of each type)

  • Astrocytes: Supportive cells that maintain the blood-brain barrier, regulate blood flow, and contribute to the repair and scarring process of the brain after injury.

  • Oligodendrocytes: Responsible for the formation of myelin sheaths around axons in the central nervous system, which increases the speed of electrical impulse conduction.

  • Schwann cells: Similar to oligodendrocytes, but they myelinate axons in the peripheral nervous system, aiding in regeneration and repair of peripheral nerves.

  • Microglia: The immune cells of the brain that protect against pathogens, clear debris, and modulate inflammation.

 

II. The Nervous System Extends throughout the Body (Neuroanatomy II PowerPoint)

--What are the 2 components of the central nervous system?

  • brain and spinal cord

--What is a nerve?

  • A nerve is a bundle of axons enclosed in a protective sheath, which transmits signals between the central nervous system and various parts of the body; located outside of CNS

--The 2 divisions of the PNS are the somatic nervous system and the autonomic nervous system.

            --What are the 2 anatomical groups of nerves of the somatic nervous system?

  •    cranial nerves and spinal nerves

            --What are the 2 divisions of the autonomic nervous system?

  • sympathetic and parasympathetic nervous system

 

Somatic nervous system

--Figure 1.7 Cranial nerves:  Be able to identify cranial nerves by number and know basic functions of each

  1. olfactory: responsible for the sense of smell, transmitting information from the nasal cavity to the brain

  2. optic: responsible for vision, transmitting information from the retina to the brain

  3. oculomotor: controls most of the eye's movements

  4. trochlear: also involved in eye movement

  5. trigeminal: provides sensation to the face and controls the muscles for chewing

  6. abducens: also involved in eye movement

  7. facial: responsible for facial expressions and provides taste sensations to the anterior two-thirds of the tongue

  8. vestibulocochlear: responsible for hearing and balance, transmitting sound and equilibrium information from the inner ear to the brain

  9. glossopharyngeal: responsible for swallowing, salivation, and providing taste sensations from the posterior one-third of the tongue; throat muscles

  10. vagus: responsible for conveying information from internal organs and regulating functions such as heart rate, gastrointestinal activity, and respiratory rate

  11. spinal accessory: responsible for controlling the muscles of the neck

  12. hypoglossal: responsible for controlling tongue movements, essential for speech and swallowing

--Spinal nerves:  how many pairs? 

  • 31 pairs of spinal nerves

Know the divisions by spinal cord segment (8 cervical, etc.)

  • 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

            --Each has motor and sensory component

 

Autonomic nervous system

--connects to viscera

--What does “autonomic” (autonomous) refer to?

  • Functions independently of conscious control, regulating involuntary bodily functions such as heart rate, digestion, and respiratory rate

--Be able to differentiate sympathetic vs parasympathetic divisions of the autonomic nervous system (Figure 1.9 and table, slides 17 and 18 of Neuroanatomy II PowerPoint)

  • sympathetic division: consists of the sympathetic ganglia and axons that lead to the organs; helps prepare body for “fight or flight”

    • functions:

      • dilates/opens pupils

      • inhibits salivation

      • relaxes airways

      • accelerates heartbeat

      • stimulates secretion by sweat glands

      • stimulates glucose production and release

      • inhibits digestion

      • stimulates secretion of epinephrine and norepinephrine

      • constricts blood vessels in skin

      • relaxes bladder

      • stimulates ejaculation

    • most signals originate from thoracic spinal nerves

  • parasympathetic division: arises from both the brain and sacral parts of spinal cord; helps prepare body to “rest and digest”

    • functions:

      • constricts pupils

      • stimulates salivation

      • constricts airways

      • slows heartbeat

      • stimulates digestion

      • stimulates gallbladder to release bile

      • dilates blood vessels in intestines

      • dilates blood vessels in skin

      • contracts bladder

      • stimulates erection and clitoral engorgement

 

--Be able to recognize horizontal vs sagittal vs coronal planes of section

--Define and differentiate:  nuclei vs ganglia; tracts vs nerves

  • nuclei: clusters of neurons in CNS

  • ganglia: clusters of neurons in PNS

  • tracts: bundles of axons in the CNS

  • nerves: bundles of axons in the PNS

--What characterizes gray matter versus white matter?

  • gray matter: contains neuronal cell bodies, dendrites, and unmyelinated axons, primarily involved in processing and transmitting information within the brain and spinal cord

  • white matter: contains myelinated axons that connect different regions of gray matter, facilitating communication between various areas of the brain and spinal cord

--What is the corpus callosum?

  • The corpus callosum is a large band of neural fibers located beneath the cerebral cortex that connects the left and right hemispheres of the brain, allowing for interhemispheric communication and coordination of sensory and motor functions

--Know the divisions of the nervous system (slide 28, Neuroanatomy II PowerPoint)

  • frontal lobe: responsible for executive functions such as decision making, problem solving, and planning, as well as controlling voluntary movements

  • precentral gyrus: primary motor cortex (located in frontal lobe)

  • central sulcus: a prominent groove that separates the frontal lobe from the parietal lobe, playing a crucial role in demarcating the areas responsible for movement and sensory information

  • postcentral gyrus: primary somatosensory cortex (located in parietal lobe)

  • parietal lobe: involved in processing sensory information from the body, including touch, temperature, and pain, and is also important for spatial awareness and navigation

  • occipital lobe: the region at the back of the brain that is primarily responsible for visual processing, integrating information from the eyes to facilitate perception of colors, shapes, and motion

  • temporal lobe: responsible for processing auditory information and is also involved in memory and emotion regulation, housing structures critical for language comprehension and the formation of new memories

  • sylvian fissure: the cleft that separates the temporal lobe from the frontal and parietal lobes, playing a key role in language processing and sensory integration, particularly for auditory stimuli

  • cerebellum: the structure located at the base of the brain that coordinates voluntary movements, balance, and posture, while also playing a role in motor learning and cognitive functions

  • brainstem: the lower extension of the brain that connects to the spinal cord, controlling vital autonomic functions such as heart rate, breathing, and sleep cycles, and serving as a conduit for information between the brain and the body

  • olfactory bulb: a neural structure involved in the sense of smell, located at the front of the brain, where sensory input from the nasal cavity is processed before being sent to other brain regions for further interpretation

 

III. The Brain Shows Regional Specialization of Functions (Neuroanatomy III PowerPoint)

--The cerebral cortex has 6 layers:

  • layer I outermost, few cell bodies

  • layers V and VI: neurons with large cell bodies

  • pyramidal cell: most prominent in cerebral cortex

  • cortical columns: vertical structures that are often involved in processing specific types of information, contributing to the functional organization of the cortex

--Basal ganglia:  be able to recognize the components; these structures are involved in Parkinson’s Disease and Huntington’s Disease

  • caudate nucleus: one of the main substructures of the basal ganglia, playing a critical role in motor control and learning

  • putamen: another key component of the basal ganglia, it is involved in the regulation of movement and various aspects of cognitive and emotional behavior

  • globus pallidus: another vital part of the basal ganglia that contributes to the regulation of voluntary movements, as well as modulating the actions of the motor cortex

--Limbic system:  be able to recognize the components

  • amygdala: responsible for processing emotions such as fear and pleasure, as well as playing a key role in memory formation

  • hippocampus: involved in the formation of new memories and spatial navigation, as well as influencing emotional responses

  • fornix: a C-shaped bundle of nerve fibers that connects the hippocampus to other parts of the limbic system, playing a crucial role in the retrieval of memories

  • cingulate gyrus: a part of the cerebral cortex that is involved in emotion regulation, impulse control, and the processing of pain, helping to connect behavioral responses to motivational stimuli

  • olfactory bulb: an important structure involved in the sense of smell, which processes odor information and sends it to the brain for interpretation

            --What are the functions of the hypothalamus?  The thalamus?

  • hypothalamus: a crucial brain structure that regulates essential bodily functions such as temperature, hunger, thirst, and sleep, while also playing a key role in the hormonal regulation of the body through its connection to the pituitary gland

  • thalamus: a relay station for sensory information, the thalamus processes and transmits sensory signals to the appropriate areas of the cerebral cortex, contributing to functions such as perception, attention, and consciousness

--What are the structural components of the midbrain?

  • tectum: the dorsal region of the midbrain

    • superior colliculi: responsible for processing visual information and coordinating eye movements

    • inferior colliculi: involved in processing auditory information and plays a key role in the localization of sound

  • tegmentum: the ventral region of the midbrain, playing a crucial role in arousal, attention, and modulation of reflexes

    • substantia nigra: a critical structure in the midbrain that produces dopamine, playing a vital role in movement control and reward processing; considered part of basal ganglia

    • reticular formation: a network of neurons essential for regulating wakefulness, sleep, and levels of arousal

    • periaqueductal gray: a cluster of gray matter around the cerebral aqueduct in the midbrain, involved in pain perception

    • fiber tracts: bundles of axons that transmit signals between different regions of the central nervous system, playing a crucial role in communication between the brain and the spinal cord

--Hindbrain:  What are the basic functions of the cerebellum?  Pons?  Medulla?

  • cerebellum: attached to brainstem, crucial for motor coordination and control, participates in some types of learning

  • pons: a structure that serves as a relay station, facilitating communication between the cerebellum and the rest of the brain, and also regulates functions such as breathing and sleep; contains sensory and motor nuclei; origin of some cranial nerves

  • medulla: marks transition from brain to spinal cord, responsible for regulating vital autonomic functions such as heart rate, blood pressure, and respiration; also plays a role in reflex actions like swallowing and coughing; origin of some cranial nerves

 

IV. Specialized Support Systems Protect and Nourish the Brain (Neuroanatomy III PowerPoint)

--What are the 3 meninges?

  • dura mater: tough outermost layer

  • arachnoid mater: middle layer with a web-like structure that cushions the brain, filled with cerebrospinal fluid (CSF)

  • pia mater: delicate innermost layer that adheres closely to the surface of the brain and spinal cord.

--CSF:  provides cushioning, nutrients

  • contained in ventricular system: system of fluid-filled cavities in brain

            --flows from lateral ventricles to 3rd ventricle to 4th ventricle (via cerebral aqueduct)

            --exits from 4th ventricle to flow over brain

            --CSF produced by choroid plexus in lateral ventricles (filtrate of blood)

            --What is hydrocephalus?  Be familiar with the interesting adult case discussed in class.

  • hydrocephalus: a condition characterized by an accumulation of cerebrospinal fluid (CSF) within the ventricles of the brain, often leading to increased intracranial pressure and potentially causing neurological damage; can be treated by placing a shunt to drain CSF

  • adult case study: 44 year old patient presents with massive ventricular enlargement but has normal social functioning

 

--Glymphatic system

            --glia participate in this system:

  • CSF enters brain through aquaporins in the end feet of astrocytes surrounding the arterioles

            --drainage of waste-bearing CSF-derived fluids from brain

            --operative primarily during sleep, impaired in people with sleep disorders (e.g. apnea)

--clinical implications for e.g. Alzheimer’s Disease:

  • Reduced clearance of toxic proteins such as amyloid-beta, contributing to neurodegeneration and cognitive decline

 

--Brain is ~2% of human body; what percentage of body’s energy does it use?

  • The brain utilizes approximately 20% of the body's total energy supply, highlighting its significant demand for metabolic resources

--What is the blood-brain barrier?

  • The blood-brain barrier is a specialized network of blood vessels and cells that serves to protect the brain from harmful substances while allowing essential nutrients to pass through; movement of substances from blood vessels to brain is more difficult than in other parts of the body, ensuring that only select materials can penetrate this barrier and reach the neural tissue

            --BBB protects brain from toxins

            --BBB makes drug delivery to brain difficult

            --can be compromised in some disease states

--Stroke:

            --What is stroke?

  • a stroke occurs when there is a disruption of blood flow to a certain part of the brain, leading to damage or dysfunction of the brain tissue in that area

            --What are the 2 types of stroke?

  • hemorrhagic stroke: occurs when a blood vessel in the brain ruptures, causing bleeding in or around the brain; can result from various factors, including high blood pressure and aneurysms

  • ischemic stroke: occurs when a blood vessel supplying blood to the brain is obstructed, typically by a blood clot or a buildup of fatty deposits (atherosclerosis), which can lead to tissue death in the affected area

  • Transient Ischemic Attack (TIA): often termed a "mini-stroke," this occurs when there is a temporary decrease in blood supply to part of the brain, leading to brief, stroke-like symptoms that resolve within 24 hours. It is a warning sign for future strokes.

            --What are the 5 warning signs of stroke?

  • Sudden numbness or weakness in the face, arm, or leg, especially on one side of the body.

  • Confusion or difficulty speaking or understanding speech.

  • Trouble seeing in one or both eyes.

  • Difficulty walking, dizziness, loss of balance, or lack of coordination.

  • A sudden, severe headache with no known cause.