Spinal Cord Anatomy and Function Quiz

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Questions and Answers

What structure protects the spinal cord?

Cardiac muscle

Meninges (correct)

Vertebral column (correct)

Cranial cavity

Where is the grey matter located in the spinal cord?

Surrounding the white matter

Only in the anterior region

In the interior part (correct)

On the outer part

What is the name of the structure that connects the two sides of the grey matter?

Posterior median sulcus

Anterior median fissure

Central canal

Grey commissure (correct)

Which of the following structures is NOT part of the spinal cord's white matter arrangement?

Ventral sulcus Signup and view all the answers

What is the central canal of the spinal cord?

A hollow structure in the grey commissure Signup and view all the answers

What is the primary mechanism by which urine moves through the ureters?

Peristalsis Signup and view all the answers

Which substance is actively secreted into the nephron for urine formation?

Potassium (K+) Signup and view all the answers

What triggers the micturition reflex?

Pressure in the bladder Signup and view all the answers

How much urine does a healthy adult produce on average per day?

1-2L Signup and view all the answers

What is the function of the trigone within the urinary system?

To prevent backflow of urine Signup and view all the answers

Which of these components represents a product of protein breakdown found in urine?

Creatinine Signup and view all the answers

Which system is primarily responsible for increasing the frequency of urine flow?

Parasympathetic nervous system Signup and view all the answers

What is the capacity of a fully distended urinary bladder?

1L Signup and view all the answers

Which lobe of the brain is primarily responsible for voluntary motor function?

Frontal lobe Signup and view all the answers

Where do pain, pressure, or temperature signals synapse before reaching the postcentral gyrus?

Thalamus Signup and view all the answers

Which area of the brain processes visual input?

Occipital lobe Signup and view all the answers

What is the primary function of the insula in the brain?

Receiving taste information Signup and view all the answers

What comprises the grey matter of the cerebrum?

Dendrites and unmyelinated axons Signup and view all the answers

What is the primary function of the medulla oblongata?

Autonomic reflex center maintaining homeostasis Signup and view all the answers

Which layer of the meninges is the innermost and adheres closely to the surface of the brain and spinal cord?

Pia mater Signup and view all the answers

Which part of the spinal cord is responsible for sensory nerve input?

Dorsal roots Signup and view all the answers

How many pairs of spinal nerves are there in total?

31 Signup and view all the answers

What structure in the brain stem is referred to as the bridge due to its function?

Pons Signup and view all the answers

Which of the following correctly describes the composition of the brain?

Made up of 100 billion neurons and a trillion neuroglial cells Signup and view all the answers

What major function does the pons serve?

Coordinates respiratory activities Signup and view all the answers

Which reflex involves a sensory stimulus leading to an involuntary response?

Pupillary reflex Signup and view all the answers

What anatomical feature corresponds with limb innervation in the spinal cord?

Cervical enlargements Signup and view all the answers

Which structure is responsible for connecting the spinal cord to the rest of the brain?

Brain stem Signup and view all the answers

What is the function of the cerebrospinal fluid found in the meninges?

Protects the central nervous system and forms partitions in the skull Signup and view all the answers

Which of the following correctly summarizes the organization of spinal nerves?

31 pairs total with 7 cervical bones Signup and view all the answers

Where are the cell bodies of motor neurons located in the spinal cord?

In the horns of the grey matter Signup and view all the answers

What is the primary function of cerebrospinal fluid?

To protect the brain and spinal cord from trauma Signup and view all the answers

Which cranial nerves are primarily involved in the autonomic nervous system?

III, VII, IX, and X Signup and view all the answers

Which layer of the meninges is directly in contact with the brain?

Pia mater Signup and view all the answers

Where are the cell bodies of sympathetic neurons located?

In the lateral horn of the spinal cord between T1 and L2 Signup and view all the answers

Which of the following statements about the somatic nervous system is accurate?

It involves single neuron pathways from the CNS to the effector. Signup and view all the answers

What is the main function of the hypothalamus in the autonomic nervous system?

Integrate and relay information to other brain regions Signup and view all the answers

Which autonomic division is activated during stressful situations?

Sympathetic division Signup and view all the answers

How many pairs of cranial nerves are present in the human body?

12 pairs Signup and view all the answers

In which part of the brain does cerebrospinal fluid circulate?

Ventricles and central canal of the spinal cord Signup and view all the answers

Which of the following accurately describes the role of ependymal cells in the ventricles?

They assist in the circulation of cerebrospinal fluid. Signup and view all the answers

How does the sympathetic nervous system affect heart rate?

It increases heart rate. Signup and view all the answers

Which structure does NOT contribute to the autonomic nervous system regulation?

Somatic motor neurons Signup and view all the answers

What is the function of the parasympathetic nervous system during digestion?

Increases digestive secretion and motility. Signup and view all the answers

Which neurotransmitter is primarily associated with the sympathetic nervous system?

Norepinephrine Signup and view all the answers

What are the two main divisions of the peripheral nervous system?

The two main divisions are the somatic nervous system and the autonomic nervous system. Signup and view all the answers

How does the somatic nervous system differ from the autonomic nervous system in terms of control?

The somatic nervous system is under voluntary control while the autonomic nervous system operates involuntarily. Signup and view all the answers

What role do sensory receptors play in the peripheral nervous system?

Sensory receptors detect internal and external environmental stimuli and transmit this information to the CNS. Signup and view all the answers

What is the function of the enteric nervous system?

The enteric nervous system controls the functions of the digestive tract and regulates smooth muscle and gland activity. Signup and view all the answers

Describe the neuron structure of the autonomic nervous system.

The autonomic nervous system uses a two-neuron system with synapses occurring between the preganglionic and postganglionic neurons. Signup and view all the answers

What aspects do the sympathetic and parasympathetic divisions of the autonomic nervous system regulate?

The sympathetic division prepares the body for 'fight or flight,' while the parasympathetic division promotes 'rest and digest' functions. Signup and view all the answers

What distinguishes the actions of afferent and efferent divisions in the nervous system?

Afferent divisions transmit sensory information to the CNS, while efferent divisions carry motor commands from the CNS to effectors. Signup and view all the answers

Where are the cell bodies of autonomic neurons typically located?

The cell bodies of the first neuron are in the CNS, while those of the second are located in autonomic ganglia outside the CNS. Signup and view all the answers

How do the sympathetic and parasympathetic pathways differ in terms of neuron length?

Sympathetic pathways typically have shorter preganglionic neurons, leading to faster responses, while parasympathetic pathways have longer preganglionic neurons. Signup and view all the answers

What is the significance of myelination in the autonomic nervous system?

Myelination speeds up signal transmission; preganglionic neurons are myelinated while postganglionic neurons are unmyelinated. Signup and view all the answers

What defines non-gated ion channels and their role in the cell membrane?

Non-gated ion channels are always open and allow specific ions, particularly K+ and Cl-, to diffuse through the membrane based on concentration gradients. Signup and view all the answers

How do gated ion channels differ from non-gated ion channels?

Gated ion channels remain closed until triggered by specific stimuli, while non-gated ion channels are always open. Signup and view all the answers

What is the resting membrane potential in neurons, and what contributes to its value?

The resting membrane potential in neurons is approximately -70mV, primarily established by the differential distribution of K+ and Na+ ions and the action of the Na+/K+ pump. Signup and view all the answers

Describe the importance of K+ and Na+ concentrations in establishing resting membrane potential.

K+ is more concentrated inside the cell while Na+ is concentrated outside, leading to the diffusion of K+ out of the cell and Na+ into the cell, generating the resting membrane potential. Signup and view all the answers

What are the functional implications of having more K+ leak channels than Na+ leak channels?

The higher number of K+ leak channels allows more potassium to exit the cell, creating a greater negative charge inside and influencing the resting membrane potential. Signup and view all the answers

What are the three main components of the cardiovascular system?

The three main components are the heart, blood vessels, and blood. Signup and view all the answers

How do ligand-gated ion channels facilitate synaptic transmission?

Ligand-gated ion channels open when specific chemicals bind to them, allowing ions to flow into or out of the cell and facilitating synaptic transmission. Signup and view all the answers

Explain the primary function of the heart.

The primary function of the heart is to pump blood throughout the body, generating pressure to move the blood. Signup and view all the answers

What role do the valves in the heart serve?

The valves prevent backflow of blood, ensuring one-way flow through the heart chambers. Signup and view all the answers

Explain how voltage-gated ion channels contribute to action potentials.

Voltage-gated ion channels open in response to changes in membrane potential, allowing rapid influx of Na+ and subsequent outflow of K+, which is essential for the propagation of action potentials. Signup and view all the answers

What determines the polarity of the plasma membrane during the resting state?

The polarity of the plasma membrane during rest is determined by the concentration gradient of ions, particularly the higher intracellular K+ and the presence of negatively charged proteins inside the cell. Signup and view all the answers

Describe the difference between systemic and pulmonary circulation.

Systemic circulation delivers oxygenated blood to body tissues, while pulmonary circulation transports deoxygenated blood to the lungs for oxygenation. Signup and view all the answers

What is the cardiac cycle?

The cardiac cycle refers to the repetitive contraction (systole) and relaxation (diastole) of the heart chambers. Signup and view all the answers

Discuss the significance of the pericardium.

The pericardium protects the heart and anchors it by preventing overdistension. Signup and view all the answers

What is cardiac output and how is it calculated?

Cardiac output is the volume of blood the heart pumps per minute, calculated by the formula 'heart rate x stroke volume'. Signup and view all the answers

Identify the main differences between atria and ventricles.

Atria are thinner-walled chambers that receive blood, while ventricles have thicker walls and pump blood out of the heart. Signup and view all the answers

Explain the importance of the interventricular septum.

The interventricular septum separates the left and right ventricles, ensuring the separation of oxygenated and deoxygenated blood. Signup and view all the answers

What function do pectinate muscles serve in the heart?

Pectinate muscles aid in the expansion and contraction of the atria to improve blood force during contraction. Signup and view all the answers

Outline the pathway of blood flow from the heart to the lungs.

Blood flows from the right atrium through the tricuspid valve into the right ventricle, then exits via the pulmonary semilunar valve into the pulmonary trunk. Signup and view all the answers

What are trabeculae carnae and where are they found?

Trabeculae carnae are muscular ridges found on the inner walls of the ventricles. Signup and view all the answers

Describe the role of coronary circulation.

Coronary circulation is the flow of blood to and from the tissues of the heart muscle itself. Signup and view all the answers

What happens during diastole in the cardiac cycle?

During diastole, the heart chambers relax and fill with blood as the pressure within them decreases. Signup and view all the answers

What are fenestrated capillaries, and where are they commonly found?

Fenestrated capillaries have pores in their endothelial cells, providing high permeability. They are commonly found in areas such as the intestinal villi and the kidney's glomeruli. Signup and view all the answers

Describe the significance of interstitial fluid in capillary exchange.

Interstitial fluid bathes the cells, allowing substances to diffuse between the capillary blood and cells. It is essential for maintaining concentration gradients necessary for nutrient and gas exchange. Signup and view all the answers

How does the lymphatic system assist in maintaining homeostasis in the circulatory system?

The lymphatic system collects excess fluid from tissues and returns it to the bloodstream, preventing fluid accumulation. It plays a crucial role in maintaining blood volume and pressure. Signup and view all the answers

What is the primary function of capillary exchange, and which substances are typically involved?

Capillary exchange facilitates the movement of substances, such as oxygen, nutrients, and hormones, from the blood into tissues. It also allows for the removal of waste products like carbon dioxide. Signup and view all the answers

What role do concentration gradients play in the diffusion process during capillary exchange?

Concentration gradients drive the diffusion of substances, with molecules moving from areas of high concentration to areas of low concentration. This gradient is crucial for effective O2 and CO2 exchange. Signup and view all the answers

Explain the difference between lipid-soluble and water-soluble substances in the context of capillary diffusion.

Lipid-soluble substances like O2 and CO2 can diffuse directly through the plasma membranes of endothelial cells. In contrast, water-soluble molecules such as glucose diffuse through intercellular spaces or fenestrations. Signup and view all the answers

What causes oedema in body tissues, and what factors contribute to its development?

Oedema is caused by excess fluid in body tissues, often due to capillary leakage, heart failure, or issues with the lymphatic system. Factors such as kidney disease, pregnancy, and high salt intake can also contribute. Signup and view all the answers

What are sinusoidal capillaries, and where is their structure particularly beneficial?

Sinusoidal capillaries are characterized by large diameters and incomplete walls, allowing large molecules and cells to cross easily. They are particularly beneficial in the liver and endocrine glands. Signup and view all the answers

Identify the main components of the lymphatic system.

The main components of the lymphatic system include lymphoid organs like the spleen, thymus, and tonsils, as well as lymphatic vessels, nodes, and the fluid called lymph. Signup and view all the answers

How does the cardiovascular system interact with the lymphatic system to prevent fluid accumulation?

The cardiovascular system pumps blood through capillaries, where fluid can leak into interstitial spaces. The lymphatic system collects this excess fluid and returns it to venous circulation, preventing swelling. Signup and view all the answers

What are the two types of reflexes associated with the spinal cord?

The two types of reflexes are spinal reflexes and cranial reflexes. Signup and view all the answers

Describe the role of the Golgi tendon reflex.

The Golgi tendon reflex protects muscles from excessive force by inhibiting muscle contraction. Signup and view all the answers

What is the main function of the cerebellum?

The cerebellum coordinates voluntary movements and maintains posture and balance. Signup and view all the answers

What is the function of the medulla oblongata in the autonomic nervous system?

The medulla oblongata regulates vital autonomic functions like heart rate and breathing. Signup and view all the answers

How does the diameter of the spinal cord vary along its length?

The spinal cord's diameter is wider in the cervical and lumbar regions due to neural enlargements. Signup and view all the answers

What are meninges and their primary functions?

Meninges are protective connective tissue layers covering the brain and spinal cord. Signup and view all the answers

Identify the three layers of meninges from outermost to innermost.

The three layers are dura mater, arachnoid mater, and pia mater. Signup and view all the answers

What is the role of the pons in brain function?

The pons connects different parts of the brain and regulates vital functions like respiration. Signup and view all the answers

What structure in the spinal cord contains the central canal?

The central canal is located within the grey matter of the spinal cord. Signup and view all the answers

Describe the composition of white matter in the spinal cord.

White matter in the spinal cord consists mainly of myelinated nerve tracts. Signup and view all the answers

How many pairs of spinal nerves emerge from the spinal cord?

There are 31 pairs of spinal nerves that emerge from the spinal cord. Signup and view all the answers

What type of neurons travel through the ventral roots of the spinal cord?

Motor neurons, both somatic and autonomic, travel through the ventral roots. Signup and view all the answers

What initiates a voluntary reaction compared to a reflex?

A voluntary reaction is initiated by conscious thought whereas a reflex is an involuntary response to a stimulus. Signup and view all the answers

What is the conus medullaris?

The conus medullaris is the pointed end of the spinal cord. Signup and view all the answers

Study Notes

Urine Formation and Composition

Urine diffuses into the nephron lumen passively, whereas H+, K+, and penicillin are actively secreted into the nephron.
Pressure drives urine through the nephron's lumen; peristalsis moves urine from ureters to bladder, facilitating a steady flow every few seconds.
Parasympathetic stimulation increases urine transport frequency (rest and digest), while sympathetic stimulation decreases it (fight or flight).
Trigone pressure in the ureters prevents urine backflow.

Daily Urine Production

Urine constitutes about 1% of the filtrate, with 1-2 liters produced per day.
Urine composition varies based on the body's needs and includes:
- Urea, uric acid, ammonia, creatinine, H+, K+, bile pigments, drugs, and toxins (e.g., penicillin).
Specific concentrations of urine constituents:
- 0.05% ammonia, 0.18% sulphate, 0.12% phosphate, 0.6% chloride, 0.1% magnesium, 0.015% calcium, 0.6% potassium, 0.1% sodium, 0.1% creatinine, 0.03% uric acid, 2% urea, and 95% water.

Micturition Reflex

Continuous urine flow from ureters to the bladder contrasts with intermittent flow from the bladder to urethra.
Bladder capacity approximates 1 liter.
Micturition is the process of urine elimination from the bladder, initiated by stretch receptors that signal the central nervous system.
Voluntary control through the central nervous system regulates the external urethral sphincter, allowing urination alongside bladder contraction.

Nervous System Terminology

Neurons are the fundamental functional units of the nervous system; neuroglia supports neuron functions.
Axons are nerve fibers, while nerves are bundles of axons with protective sheaths.
Sensory receptors detect various stimuli (temperature, pain, touch, light, sound, odor).
Action potentials serve as electrical signals for information transmission.
Effector organs are tissues where actions occur, and synapses are neuron junctions with other cells.

Functions of the Nervous System

Acetylcholine diffuses from the synaptic cleft into the extracellular fluid.

Spinal Cord Overview

The spinal cord connects the brain to lower body structures, extending from the foramen magnum to the second lumbar vertebra.
It is protected by the vertebral column and meninges, composed of connective tissue.
Grey matter is located internally, with white matter externally arranged into distinct horns (posterior, lateral, anterior).
Anterior median fissure and posterior median sulcus are depressions in the white matter; the central canal is located within the grey commissure.

Reflex Actions

Reflexes are involuntary and faster than voluntary reactions, which involve sensory stimuli and include repetitive learning such as catching or dodging objects.

Spinal Nerves and Regions

The spinal cord consists of cervical, thoracic, lumbar, sacral, and coccygeal regions.
There are a total of 31 pairs of spinal nerves:
- Cervical: 8 pairs
- Thoracic: 12 pairs
- Lumbar: 5 pairs
- Sacral: 5 pairs
- Coccygeal: 1 pair
Spinal nerve and vertebral bone count differs due to C1 emerging above the first cervical vertebra.

Meninges Structure

Meninges cover the CNS: protect structures, contain cerebrospinal fluid, and form cranial partitions.
Dura mater is the thickest and outermost layer; arachnoid mater contains cerebral blood vessels and CSF; pia mater closely adheres to the brain and spinal cord, having numerous blood vessels.

Brain Structure and Functions

The brain, weighing 1.5 kg, consists of approximately 100 billion neurons and trillions of neuroglial cells.
Major divisions: forebrain (cerebrum, diencephalon), midbrain, hindbrain (pons, medulla oblongata, cerebellum), with the brainstem comprising the midbrain, pons, and medulla.
Medulla oblongata connects to the spinal cord, regulating autonomic functions like heart rate and respiration; it coordinates reflexes.
Pons acts as a bridge in the brainstem, facilitating communication between spinal cord and higher brain centers and regulating sleep and respiration.
The cerebellum coordinates movements and maintains balance, while the cerebral cortex processes sensory information and houses conscious awareness.### Meningeal Layers and Cerebrospinal Fluid
Arachnoid mater is located beneath the dura mater and contains the subarachnoid space filled with cerebrospinal fluid (CSF) and blood vessels.
Pia mater is the innermost meningeal layer, a fragile connective tissue closely adhering to the brain, containing small blood vessels.

Brain Ventricles

The brain contains four interconnected ventricles, lined with ependymal cells.
Lateral ventricles are the largest and extend into the cerebral hemispheres, classified as the first and second ventricles.
The lateral ventricles lead into the third ventricle, which resembles a bird's head.
The third ventricle connects to the fourth ventricle located in the brainstem, which in turn connects to the spinal cord through the central canal.

Cerebrospinal Fluid (CSF)

Most CSF is produced in the choroid plexus, composed of specialized ependymal cells and blood vessels.
CSF provides protection and buoyancy to the brain, reducing pressure on underlying structures.
The composition of CSF is similar to blood plasma but has lower protein content and differing ionic concentrations.
CSF circulates through the ventricles, central canal of the spinal cord, and subarachnoid space, aided by cilia on ependymal cells.

Cranial Nerves

There are 12 pairs of cranial nerves, named using Roman numerals, emerging directly from the brain.
These nerves carry sensory and motor information between the brain and the body.
Cranial nerves can be sensory, motor, or mixed, with different functional roles.

Functional Divisions of the Nervous System

The nervous system is divided into the autonomic nervous system (ANS) and the somatic nervous system.
ANS is responsible for involuntary actions, while the somatic system manages voluntary movements.

Autonomic vs Somatic Nervous System

Somatic nervous system controls skeletal muscle movement consciously, while ANS regulates cardiac muscle, smooth muscle, and glands unconsciously.
The somatic system involves one neuron from the CNS to the target muscle; ANS involves two neurons: a preganglionic and a postganglionic neuron.

Sympathetic and Parasympathetic Nervous Systems

Sympathetic system prepares the body for 'fight or flight' responses during stress, leading to increased heart rate, reduced digestion, and other physiological changes; known as the "E" division.
Parasympathetic system promotes 'rest and digest' functions, conserving energy and stimulating digestion; known as the "D" division.
Both systems can affect the same organs but in contrasting ways.

Anatomy of the Autonomic Nervous System

ANS consists of two neuron systems; sympathetic neurons originate between T1 and L2 (thoracolumbar division), and parasympathetic neurons arise from S2 to S4 and certain cranial nerve nuclei (craniosacral division).

Functional Generalizations

Both sympathetic and parasympathetic systems provide dual innervation and have opposing effects on various functions like heart rate, blood pressure, and digestive processes.

Regulation of the Autonomic Nervous System

ANS mostly operates through reflexes regulated by the spinal cord, brainstem, and hypothalamus.
Reflexes maintain homeostatic balance in bodily functions.
The hypothalamus integrates signals and communicates with higher brain centers to modulate responses.

CNS Components and Their Effects

Spinal cord governs autonomic reflexes for functions like urination and defecation.
Brainstem controls several reflex actions including salivation and heart rate.
The hypothalamus integrates spinal and brainstem information to inform higher brain functions.
Thoughts and emotions from the cerebrum and limbic system can influence ANS activities through the hypothalamus.

Components of the Cardiovascular System

Heart functions as a pump for generating blood pressure to circulate blood throughout the body.
Blood vessels include arteries, veins, and capillaries, serving as conduits for blood transportation.
Blood transports dissolved or suspended substances, aiding in distribution within the body.

Functions of the Cardiovascular System

Transport:
- Gases: Oxygen, carbon dioxide, nitrogen.
- Nutrients: Glucose, amino acids, vitamins, proteins, and lipids.
- Metabolic Waste: Urea, uric acid, creatine, ammonium ions.
- Regulatory Molecules: Hormones and enzymes.
- Processed Molecules: Includes proteins, carbohydrates, and lipids.
Protection:
- Involves inflammation, phagocytosis, antibodies, and platelets for clotting.
Regulation:
- Maintains fluid balance, pH, body temperature, blood pressure, and nutrient exchange between blood and cells.

Heart Overview

Function:
- Acts as a pump, generating pressure for blood movement and maintaining a separate pulmonary and systemic circulation.
- Ensures one-way blood flow due to pressure differences.
- Regulates blood supply based on bodily needs (homeostasis).
Protection:
- Shielded by the rib cage, protective membranes, and fluid-filled pericardium.
Location:
- Situated in the thoracic cavity, between the lungs and above the diaphragm, about the size of a closed fist (300g).

Pericardium

Fibrous Pericardium: Tough outer layer preventing overexpansion, anchoring the heart.
Serous Pericardium:
- Inner layer composed of parietal and visceral layers, creating a pericardial cavity filled with fluid to reduce friction.
Infection of the pericardium is termed pericarditis.

Heart Morphology

Features grooves (sulci) such as the coronary sulcus and interventricular sulci, which separate chambers.
Contains pericardial and epicardial fat that cushion and protect the heart.
Atria (collecting chambers) have thinner walls while ventricles (discharging chambers) have thicker walls.

Heart Wall Structure

Comprises three layers:
- Epicardium: Visceral pericardium, providing a smooth surface.
- Myocardium: Thick, muscular layer enabling contraction.
- Endocardium: Smooth inner surface lining heart chambers and associated with valves.

Heart Chambers

Right Atrium: Thin-walled, receives deoxygenated blood via the superior/inferior vena cava and coronary sinus.
Right Ventricle: Pumping chamber with thicker walls; pushes blood through the pulmonary trunk.
Left Atrium: Thin-walled, receives oxygenated blood from lungs through pulmonary veins.
Left Ventricle: Thickest chamber; pumps oxygenated blood into systemic circulation via the aorta.

Great Blood Vessels

Blood enters right atrium via
- Superior and inferior vena cava (deoxygenated) and coronary sinus.
Left atrium receives oxygenated blood from the lungs via pulmonary veins.
Right ventricle sends blood to lungs via pulmonary trunk.
Left ventricle sends blood to body via the aorta.

Heart Valves

Atrioventricular Valves: Located between atria and ventricles, prevent backflow; right (tricuspid) has three cusps, left (bicuspid) has two.
Semilunar Valves: Located at the base of vessels exiting ventricles; prevent backflow of blood using cup-shaped structures (pulmonary and aortic valves).
Valves connected to papillary muscles via chordae tendineae to maintain structural integrity.

Blood Flow Pathway

Deoxygenated blood: Superior/inferior vena cava → Right atrium → Tricuspid valve → Right ventricle → Pulmonary semilunar valve → Pulmonary trunk → Lungs.
Oxygenated blood: Lungs → Pulmonary veins → Left atrium → Bicuspid valve → Left ventricle → Aortic semilunar valve → Aorta.

Circulation Types

Pulmonary Circulation: Transports deoxygenated blood to lungs for oxygenation; features double circulation in one cardiac cycle.
Systemic Circulation: Delivers oxygenated blood to body tissues; involves returning deoxygenated blood to the heart.
Coronary Circulation: Specialized part of systemic circulation catering to the heart muscle itself.

Cardiac Cycle

Composed of systole (contraction) and diastole (relaxation) affecting blood movement.
Cardiac output is the product of heart rate and stroke volume, averaging 5-6 L/min at rest.
Autonomic nervous system regulates blood pressure and flow to meet tissue demands.

Capillary Exchange

Exchange occurs through interstitial fluid; substances move via diffusion based on concentration gradients.
Oxygen and Nutrients: Diffuse from capillaries to cells.
Carbon Dioxide: Moves in the opposite direction, from cells to blood.
Capillaries allow variable exchange rates: lipid-soluble substances through membranes, water-soluble via intercellular spaces.

Lymphatic System

Comprises lymphoid organs (spleen, thymus, tonsils) and lymphatic vessels.
Lymph is crucial for fluid balance and protecting against interstitial fluid accumulation.

Link Between Cardiovascular and Lymphatic Systems

Lymphatic capillaries pick up excess fluid, preventing swelling and maintaining blood volume and pressure.
Essential for homeostasis; edema (swelling) indicates fluid accumulation due to various health issues.### Peripheral Nervous System
Comprised of sensory receptors, cranial nerves (12 pairs), spinal nerves (31 pairs), ganglia, and plexuses.
Sensory receptors gather information from the environment and relay it to the central nervous system (CNS).
Cranial nerves originate from the brain, while spinal nerves extend from the spinal cord.
Ganglia are clusters of neuron cell bodies outside the CNS.
Plexuses are intricate networks of axons located outside the CNS.

Functional Divisions of the Nervous System

The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS), which interact to process sensory information and elicit motor responses.
The PNS is categorized into:
- Somatic nervous system: voluntary control, connects CNS to skeletal muscles via a single neuron system.
- Autonomic nervous system: involuntary control, consists of sympathetic (fight or flight) and parasympathetic (rest and digest) divisions.
- Enteric nervous system: regulates gastrointestinal functions independently.

Somatic vs Autonomic Nervous System

Somatic System:
- Operates voluntarily and consciously.
- Uses a single motor neuron system to stimulate skeletal muscles.
- Motor neuron cell bodies are housed in the CNS.
Autonomic System:
- Functions involuntarily and unconsciously.
- Utilizes a two-neuron system (preganglionic and postganglionic) to target smooth muscle, cardiac muscle, or glands.
- The first neuron cell body is in the CNS, the second in an autonomic ganglion.

Enteric Nervous System

Comprised of nerve plexuses within the digestive tract for local control.
Connects sensory neurons from the digestive system to the CNS and motor neurons from the CNS to the digestive tract.
Controls smooth muscle contractions and glandular secretions of the digestive system while monitoring intestinal contents.

Sensory vs Motor Division

Sensory Division (afferent):
- Detects environmental stimuli and transmits signals to the CNS.
- Composed of specialized sensory receptors and sensory neuron cell bodies located outside the CNS.
Motor Division (efferent):
- Transmits signals from the CNS to effectors (muscles and glands).
- Motor neuron cell bodies are situated within the CNS.

Autonomic Nervous System (Motor Division)

Sympathetic Division:
- Activates the fight or flight response; originates from the thoraco-lumbar region.
- Prepares the body for immediate physical action with a rapid response pathway.
Parasympathetic Division:
- Facilitates rest and recovery processes in the body.

Ion Channels

Non-gated (leak) ion channels remain open, allowing ion flow based on concentration gradients.
Gated ion channels require stimuli to open:
- Ligand-gated channels respond to chemical signals.
- Voltage-gated channels respond to changes in membrane charge.
- Other channels respond to stimuli like temperature or pressure.

Resting Membrane Potential

Defined as the voltage difference across a cell membrane at rest, typically around -70mV in neurons.
Caused by the unequal distribution of ions, mainly due to K+ leakage and Na+/K+ pump activity.
This polarization is critical for action potential generation.

Establishing Resting Membrane Potential

High K+ concentration inside the cell and Na+ concentration outside the cell.
Cell membrane is more permeable to K+, leading to K+ efflux and creating a negative charge inside the cell.

Reaction vs Reflex

Reactions are voluntary and slower; initiated by sensory stimuli and involve CNS processing (e.g., catching a ball).
Reflexes are automatic, rapid responses occurring without conscious thought.

Spinal Cord Overview

Extends from the foramen magnum to the first or second lumbar vertebrae, categorized into regions (cervical, thoracic, lumbar, sacral, coccygeal).
Composed of 31 pairs of spinal nerves, including cervical (8), thoracic (12), lumbar (5), sacral (5), and coccygeal (1).

Meninges

Protective connective tissue layers surrounding the spinal cord and brain, including three layers: dura mater, arachnoid mater, and pia mater.
Dura mater is the outer layer, while arachnoid mater contains cerebrospinal fluid, and pia mater is the delicate inner layer close to the CNS.

Organization of Neurons in the Spinal Cord

Grey matter houses nerve cell bodies and is located centrally, while white matter contains myelinated axons surrounding it.
Sensory nerves enter via dorsal roots; motor nerves exit through ventral roots.
Autonomic and somatic motor neurons are found in specific horns of the grey matter.

Nerve Structure

Endoneurium surrounds each axon; perineurium encases fascicles of axons; epineurium surrounds entire nerves.

Brain Structure

A complex, jelly-like organ weighing approximately 1.5kg, composed of about 100 billion neurons and trillions of neuroglial cells.
Divided into forebrain (cerebrum, diencephalon), midbrain, and hindbrain (pons, medulla oblongata, cerebellum).

Brain Stem

Comprises the midbrain, pons, and medulla oblongata; connects the brain to the spinal cord.
Responsible for basic life functions and reflexes.

Medulla Oblongata

Connects directly to the spinal cord; regulates autonomic functions like heart rate and respiration.
Controls reflexes such as swallowing, coughing, and sneezing.

Pons

Acts as a bridge within the brain stem, facilitating communication between higher brain centers and the cerebellum.
Contains a sleep center and respiratory regulation mechanisms.

Cerebellum

Located inferiorly and posteriorly in the brain; plays a vital role in coordinating locomotion and balance.
Comprises an outer grey matter cortex and an inner white matter medulla, significantly smaller than the cerebrum.

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Description

Test your knowledge on the structure and function of the spinal cord with this quiz. Explore key concepts such as the protective structures of the spinal cord, the location and significance of grey matter, and the role of the central canal. Challenge yourself with questions on the anatomy and mechanisms related to urine movement as well.