BISC 205 Respiratory - Muscular System & Movement

What is a neuron?

A neuron is the structural and functional unit of the nervous system. It is a specialized nerve cell responsible for receiving, processing, and transmitting information through electrical and chemical signals.

What are the five major parts of a neuron?

Dendrites, cell body (soma), axon hillock, axon, and synapses.

What is the function of dendrites?

Dendrites are highly branched extensions of the cell body that receive signals from other neurons and transmit them toward the soma.

What is the function of the cell body (soma)?

The soma contains the nucleus and most cellular organelles. It maintains the neuron and supports its metabolic functions.

What is the axon hillock?

The region where the axon connects to the soma. It integrates incoming electrical signals and initiates an action potential when the combined signal reaches threshold.

What is the function of the axon?

The axon is a long extension that conducts action potentials away from the cell body toward synaptic terminals and other target cells.

What is a synapse?

A junction where a neuron communicates with another neuron or an effector cell, usually by releasing chemical neurotransmitters.

What are glial cells?

Non-neuronal cells that support, protect, insulate, nourish, and maintain neurons. Important examples include astrocytes, oligodendrocytes, and Schwann cells.

What are oligodendrocytes?

Glial cells found in the CNS that form myelin sheaths around neuronal axons, providing electrical insulation.

What are Schwann cells?

Glial cells found in the PNS that form myelin sheaths around peripheral neuronal axons, providing electrical insulation.

What is the purpose of myelin sheaths?

Myelin electrically insulates axons and helps action potentials travel rapidly and efficiently along neurons.

What are astrocytes?

Star-shaped glial cells in the CNS that support neurons, maintain the blood-brain barrier, contribute to immunity, provide metabolic support, and assist with tissue repair.

What are the two main divisions of the nervous system?

Central nervous system (CNS), consisting of the brain and spinal cord, and peripheral nervous system (PNS), consisting of nerves outside the CNS.

What are the three components of nervous-system information processing?

Sensory input pathway, integrating system, and motor output pathway. Sensory receptors detect changes, the CNS processes information, and motor neurons activate effectors.

What is the sensory input pathway?

Sensory receptors detect internal or external stimuli. Afferent neurons transmit information toward the CNS for processing.

What is an afferent neuron?

A sensory neuron that carries electrical impulses from sensory receptors toward the CNS. Remember: afferent arrives.

What is an integrating system?

The CNS processes sensory information and determines an appropriate response. Interneurons form neural circuits that connect sensory and motor pathways.

What is the motor output pathway?

Efferent neurons carry signals away from the CNS to effector organs such as skeletal muscles, glands, and internal organs.

What is an efferent neuron?

A motor neuron that carries impulses away from the CNS toward an effector. Remember: efferent exits.

What are photoreceptors?

Sensory receptors activated by light, allowing the detection of visual stimuli.

What are mechanoreceptors?

Sensory receptors that respond to mechanical stimuli such as touch, pressure, vibration, and stretch.

What are chemoreceptors?

Sensory receptors that detect chemicals, including chemical stimuli involved in taste and smell.

What are thermoreceptors?

Sensory receptors that detect changes in temperature, including heat and cold.

What are nociceptors?

Sensory receptors that detect potentially damaging stimuli associated with pain.

What are baroreceptors?

Specialized mechanoreceptors located in the carotid sinus and aortic arch that detect changes in blood pressure.

What are the three structural types of vertebrate neurons?

Multipolar, bipolar, and pseudounipolar neurons. They differ in the number and arrangement of processes extending from the cell body.

What is a multipolar neuron?

A neuron with multiple short dendrites and one long axon extending from the soma. Typically associated with motor neurons and most interneurons.

What is a bipolar neuron?

A neuron with one dendrite and one axon extending in opposite directions from the cell body. Found among specialized neurons such as those in the retina.

What is a pseudounipolar neuron?

A neuron with a single process branching into long sensory and shorter central portions, without dendrites extending directly from the soma. Typically associated with sensory neurons.

What are four ways the CNS is protected?

1. Skull and vertebral column. 2. Protective meninges. 3. Cushioning cerebrospinal fluid. 4. Physiological separation by the blood-brain barrier.

How do skeletal structures protect the CNS?

The skull protects the brain, while the vertebral column protects the spinal cord. These structures are cartilaginous in cartilaginous fish and primarily bony in most other vertebrates.

What are the meninges?

One or more layers of protective connective tissue surrounding the brain and spinal cord.

What are the two major functions of the meninges?

1. Work with cerebrospinal fluid to protect the CNS from mechanical damage. 2. Provide a supportive framework for cerebral and cranial blood vessels.

What meninges are present in fish?

Fish possess a single thin protective membrane called the primitive meninx.

What meninges are present in amphibians and non-avian reptiles?

Two meninges: a thick outer dura mater and a thin secondary meninx.

What meninges are present in birds and mammals?

Three meninges: outer dura mater, middle web-like arachnoid mater, and inner thin pia mater.

What is cerebrospinal fluid (CSF)?

A fluid derived primarily from filtered blood plasma, found in brain cavities, around the brain and spinal cord, and within the spinal cord's central canal.

What are the four major functions of CSF?

1. Absorbs shocks and cushions the CNS. 2. Transports nutrients and hormones. 3. Removes cerebral metabolic wastes. 4. Regulates intracranial pressure.

What is the blood-brain barrier (BBB)?

A highly selective semipermeable barrier formed by tight junctions between endothelial cells lining brain capillaries. It restricts movement of substances from blood into CNS tissue.

What substances does the BBB restrict?

Pathogens, many blood solutes, and large hydrophilic molecules are restricted from entering the CNS.

What substances can cross the BBB?

Small hydrophobic molecules such as O2, CO2, and certain hormones can diffuse through. Glucose crosses using specific transport proteins.

How do astrocytes maintain the BBB?

Astrocytes support the structural integrity and normal functioning of the blood-brain barrier.

What structural and immune functions do astrocytes perform?

They provide physical support for CNS neurons and help defend against pathogens, contributing to nervous-system immunity.

How do astrocytes influence myelination?

Astrocytes promote the myelinating activity of oligodendrocytes within the CNS.

How do astrocytes supply neurons with energy?

Astrocytes take up glucose from the bloodstream, metabolize it into lactate, and transport lactate to neurons as an energy source.

How do astrocytes assist with nervous-system repair?

They form glial scars that seal damaged regions and help prevent inflammation and tissue damage from spreading.

What are the two subdivisions of the PNS?

Somatic nervous system and autonomic nervous system.

What is the somatic nervous system?

The PNS division primarily responsible for voluntary movements. It includes neurons associated with skeletal muscles and skin.

What is the autonomic nervous system (ANS)?

The PNS division responsible for involuntary functions such as heart rate, digestion, blood vessel diameter, breathing regulation, salivation, and urination.

What are the two divisions of the autonomic nervous system?

Sympathetic division, associated with fight-or-flight, and parasympathetic division, associated with rest-and-digest.

What is the sympathetic nervous system?

The fight-or-flight division, preparing the body for activity by increasing heart rate, dilating pupils, constricting certain blood vessels, releasing liver glucose, and suppressing digestion.

What is the parasympathetic nervous system?

The rest-and-digest division, promoting relaxation by lowering heart and breathing rates, constricting pupils, promoting vasodilation, and stimulating digestive organs.

What two neurons make up a typical autonomic motor pathway?

A preganglionic neuron extending from the CNS to an autonomic ganglion and a postganglionic neuron extending from the ganglion to an effector organ.

What is a preganglionic neuron?

An autonomic neuron whose cell body is located in the CNS and whose axon terminates in an autonomic ganglion.

What is an autonomic ganglion?

A cluster of peripheral neuronal cell bodies and dendrites where preganglionic neurons synapse with postganglionic neurons.

What is a postganglionic neuron?

An autonomic neuron whose cell body is in an autonomic ganglion and whose axon extends to an effector organ.

Compare preganglionic and postganglionic lengths in the sympathetic division.

Sympathetic pathways generally have short preganglionic neurons and long postganglionic neurons.

Compare preganglionic and postganglionic lengths in the parasympathetic division.

Parasympathetic pathways generally have long preganglionic neurons and short postganglionic neurons.

What neurotransmitter is released by preganglionic neurons in both ANS divisions?

Acetylcholine (ACh). It binds to nicotinic receptors on postganglionic neurons in autonomic ganglia.

What are nicotinic acetylcholine receptors?

Ionotropic, ligand-gated ion channels that bind ACh. Their opening allows net Na+ entry, rapidly depolarizing the postsynaptic neuron. Their effect is excitatory.

What neurotransmitter is typically released by parasympathetic postganglionic neurons?

Acetylcholine (ACh), which binds to muscarinic receptors on effector organs.

What are muscarinic acetylcholine receptors?

Metabotropic G-protein-coupled receptors activated by ACh. They produce slower responses that may be excitatory or inhibitory depending on receptor subtype.

How do muscarinic receptor subtypes differ?

M1, M3, and M5 stimulate phospholipase C signaling, whereas M2 and M4 inhibit adenylyl cyclase signaling.

What neurotransmitter is typically released by sympathetic postganglionic neurons?

Norepinephrine (NE), which binds to adrenergic receptors on target organs.

What are adrenergic receptors?

Metabotropic receptors activated by norepinephrine. Alpha receptors generally produce excitatory responses, whereas beta receptors are described in the lecture as generally inhibitory.

Which autonomic receptors are ionotropic versus metabotropic?

Nicotinic receptors are ionotropic ligand-gated channels. Muscarinic and adrenergic receptors are metabotropic G-protein-coupled receptors.

Compare the neurotransmitters and receptors of sympathetic versus parasympathetic pathways.

Both release ACh onto nicotinic receptors at autonomic ganglia. Parasympathetic postganglionic neurons release ACh onto muscarinic receptors; sympathetic neurons typically release NE onto adrenergic receptors.

What is a centralized nervous system?

A system in which a central brain or major integrating structure coordinates and controls much of an animal's nervous activity.

What is a decentralized nervous system?

A nervous system in which information processing and control are distributed throughout the body rather than relying exclusively on a central brain.

What nervous system do cnidarians possess?

Jellyfish and hydra possess a decentralized nerve net without a true brain. Interconnected neurons coordinate stimulus detection and simple movements.

What nervous system do echinoderms possess?

Sea stars have a decentralized nervous system consisting of a nerve ring around the mouth and five radial nerve cords, without a centralized brain.

What nervous system do flatworms possess?

A mainly centralized nervous system with a small bilobed brain, two main longitudinal nerve cords, and peripheral transverse nerves.

What nervous system do insects possess?

Both centralized and decentralized components: a brain, ventral nerve cord, and ganglia. Ganglia can independently process information and control certain movements or breathing.

What nervous system do cephalopods possess?

Octopuses and squids combine a highly developed central brain with decentralized neural networks in their arms, allowing independent local movement control.

What are important functional regions of the cephalopod brain?

Specialized lobes include the optic lobe for visual processing, vertical lobe for memory, and frontal lobe for motor control.

What characterizes the vertebrate nervous system?

A highly centralized and specialized system consisting of a CNS with brain and spinal cord and a PNS containing peripheral sensory and motor nerves.

How does nerve-cord orientation differ between many invertebrates and vertebrates?

Many invertebrates have ventral nerve cords along the belly, whereas vertebrates have a dorsal spinal cord along the back.

What is the corpus callosum?

A large bundle containing approximately 200 million myelinated nerve fibers that connects the brain's left and right cerebral hemispheres, allowing communication between them.

How do the cerebral hemispheres control opposite sides of the body?

The left hemisphere primarily controls right-side movement, while the right hemisphere primarily controls left-side movement. A left-sided stroke may impair right-side movement.

What are the four major brain sections identified in the lecture?

Cerebral cortex (cerebrum), cerebellum, diencephalon, and brainstem.

What is the cerebral cortex responsible for?

The cerebrum makes up approximately 85% of brain weight and has extensive folds. It is involved in higher-level thinking, memory, and sensory-information processing.

What are the four lobes of the cerebral cortex?

Frontal, parietal, occipital, and temporal lobes.

What are the functions of the frontal lobe?

Concentration, problem-solving, planning, organization, self-restraint, short-term memory, and speech production.

What are the functions of the parietal lobe?

Integration of sensory information, speech comprehension, taste sensation, numerical relationships and mathematics, and reading.

What are the functions of the occipital lobe?

Processing and interpretation of visual information, including sight.

What are the functions of the temporal lobe?

Processing auditory information, including hearing, and interpreting smells.

What are the functions of the cerebellum?

Maintains posture, balance, and equilibrium and coordinates precise movements, including hand-eye coordination, reaching, and visual tracking.

What structures make up the diencephalon?

Thalamus, hypothalamus, pituitary gland, and pineal gland.

What are the primary functions of the diencephalon?

Sensory relay, endocrine regulation, maintenance of homeostasis, and regulation of circadian rhythms.

What is the function of the thalamus?

Acts as a major relay station, directing sensory signals toward the cerebral cortex for processing.

What is the function of the hypothalamus?

Maintains homeostasis by monitoring body temperature, blood pressure, blood glucose, salt and mineral levels, and hormones. It also regulates pituitary hormone release.

What is the role of the pineal gland?

Produces melatonin, which helps regulate circadian rhythms and promotes sleep.

What structures make up the brainstem?

Midbrain, pons, and medulla oblongata. The brainstem connects directly to the spinal cord.

What are the major functions of the brainstem?

Controls essential involuntary physiological functions such as respiration, heart rate, blood pressure, and digestion.

What is the limbic system?

An interconnected network of brain structures involved in emotions, decisions, motivation, and memory formation.

What are the five limbic-system components emphasized in the lecture?

Hypothalamus, amygdala, hippocampus, thalamus, and olfactory bulb.

What is the function of the hippocampus?

Converts short-term memories into long-term memories and plays an important role in memory formation.

What is the function of the amygdala?

Processes emotional responses, particularly fear and aggression, and attaches emotional significance to memories.

What is the function of the olfactory bulb?

Processes sensory information involved in the sense of smell. Two olfactory bulbs are located on the underside of the brain.

What are the roles of the hypothalamus and thalamus within the limbic system?

Hypothalamus regulates homeostasis and internal conditions. Thalamus relays sensory information toward the cerebral cortex.