Principles of physiology
Chapter 9
Frontside is anterior or ventral and backside is posterior or dorsal.
Development of the human nervous system:
1. Day 20: the neural plate cells migrate toward the midline. Neural crest cells migrate with the
neural plate cells.
2. Day 23: the neural tube formation is almost complete. The neural tube becomes the central
nervous system and the neural crest becomes the peripheral nervous system.
3. 4 weeks: the embryo is showing the anterior end of the neural tube which has specialized
into three brain regions, the forebrain, midbrain and hindbrain.
4. 6 weeks: the neural tube has differentiated into the brain regions that are present at birth.
The central cavity (lumen) will become the ventricles of the brain.
5. 11 weeks: The cerebrum overgrows the rest of the brain divisions. The directional references
are different for an embryo (dorsal, rostral etc).
6. 40 weeks: the rapid growth within the rigid confines of the cranium forces it to develop a
convoluted furrowed surface
7. Child: the directions “dorsal” and “ventral” are different in the child brain because of the
flexion in the neural tube during development.
The brain is encased in bony skull, or cranium. The spinal cord runs through the vertebral column →
bony vertebrae.
Gray matter:
– Unmyelinated nerve cell bodies
– Clusters of cell bodies in the CNS are nuclei
– Dendrites
– Axon terminals
White matter
– Myelinated axons
– Axon bundles connecting CNS regions are tracts
▪ Contain very few cell bodies
Dura mater and pia mater also protects the brain → tough
,There is cerebrospinal fluid in the ventricles of the brain. There are different ventricles:
• First and second ventricles form the lateral ventricles
• → connect to the third ventricle through narrow openings
• → The cerebral aqueduct then leads form the third ventricle in the diencephalon to the fourt
ventricle in the brain stem.
• → The fourth ventricle narrows to become the central canal of the spinal cord.
Cerebrospinal fluid:
• Is a salty solution similar to plasma
• Is produced by the choroid plexus in the ventricles
- Materials selectively moved plasma to ventricles
- Water follows due to osmotic gradient
• Surrounds the entire brain
- Contained within subarachnoid space (between arachnoid membrane and pia mater)
- Flows from ventricles to subarachnoid space to return to plasma by villi
• Function in physical and chemical protection
Choroid plexus:
• Transports ions and nutrients from the blood into the cerebrospinal fluid
• Produces cerebrospinal fluid
Meninges:
• The meninges and extracellular fluid cushion the delicate brain tissue
Metabolic requirements of neural tissue
• Neurons need a constant supply of oxygen and glucose
• Brain receives 15% of blood pumped by heart → a lot
• Oxygen: passes freely across blood-brain barrier
• Glucose:
- Membrane transporters move glucose from plasma into the brain interstitial fluid
- Brain responsible for about half of body’s glucose consumption
- Progressive hypoglycemia leads to confusion, unconsciousness, and death.
The blood-brain barrier:
• Highly selective permeability of brain capillaries
• Astrocytes foot processes promote tight junctions between endothelial cells
• Protects brain from toxic water soluble compounds and pathogens
• Small lipid-soluble molecules cross the blood-brain barrier
The organization of the CNS: the spinal cord:
It contains nuclei with cell bodies of efferent neurons and tracts of axons going to and from the brain.
Dorsal root: carries sensory information to CNS. Ventral root: carries motor information to muscles
and glands. It consists of the gray matter and white matter.
• Gray matter: consists of sensory and motor nuclei
• White matter: in the spinal cord, consists of tracts of axons carrying information to and from
the brain. Ascending tracts: carry sensory information to the brain. Descending tracts: carry
commands to motor neurons.
Spinal reflexes:
The sensory information entering the spinal cord is acted on without input from the brain. However,
sensory information about the stimulus may be sent to the brain.
,There is a stimulus where the sensory receptors detect pain in the skin → these nerve signals goes
through the sensory neuron in the dorsal root ganglion → relay neuron → from here there goes a
sensation relayed to the brain and an nerve signal further to the motor neuron in the ventral root →
command to muscles or glands → response.
The brain stem:
• Midbrain: eye movement, relay signals for hearing and seeing reflexes
• Cranial nerves: 11 of 12 cranial nerves originate from the brain stem, can include sensory
fibers, efferent fibers, or both (mixed nerves). Example: vagus nerve (cranial nerve X) is a
mixed nerve.
• Medulla oblongata: Controls involuntary functions: blood pressure, breathing,
swallowing, vomiting
• Pons: Relay station, coordinates control of breathing
The diencephalon:
Lies between brain stem and the cerebrum, consisting of:
• Thalamus: sensory relay station
• Pineal gland: melatonin production → role in circadian
and circannual control
• Hypothalamus:
• Control of homeostasis
• Center for behavioral drives: for example, hunger,
thirst.
• Influences autonomic and endocrine function
• Pituitary: posterior and anterior lobes → several
controls of endocrine functions
First cranial nerve from your nose does not originate from the
brain stem.
The limbic system
Is part of the gray matter of the cerebrum
• Cingulate gyrus: plays a role in emotion
• Hippocampus: is involved in learning and memory
• Amygdala: is involved in emotion and memory
Functions of the cerebrum:
The cerebrum is the site of higher brain functions and it consists of two hemispheres connected by
corpus callosum. It has a gray matter and white matter.
Gray matter
Cerebral cortex:
• Sensory areas → perception
• Motor areas → skeletal muscle movement
• Association areas → integration of information and direction of voluntary movemet
Basal ganglia:
• Movement
Limbic system:
• Emotion, memory and learning
, White matter
• Found mostly on the interior
• Bundles of fibers connecting the different regions of the brain
Functions of the cerebellum:
• Movement coordination
The motor system (governs output from the CNS)
Three major types
• Skeletal muscle movement → somatic motor division
• Neuroendocrine signals → hypothalamus and adrenal medulla
• Visceral responses → autonomic division
Voluntary movement (is the expression of thought through action)
• Primary motor cortex
• Motor association areas
The neuroendocrine and visceral responses are coordinated in the hypothalamus and medulla
Brain function
• Sensory system
• Monitors internal and external environments
• Initiates reflex response
• Cognitive system
• Initiates voluntary responses
• Behavioral state system
• Governs sleep-wake cycles and other intrinsic behaviors
Chapter 9
Frontside is anterior or ventral and backside is posterior or dorsal.
Development of the human nervous system:
1. Day 20: the neural plate cells migrate toward the midline. Neural crest cells migrate with the
neural plate cells.
2. Day 23: the neural tube formation is almost complete. The neural tube becomes the central
nervous system and the neural crest becomes the peripheral nervous system.
3. 4 weeks: the embryo is showing the anterior end of the neural tube which has specialized
into three brain regions, the forebrain, midbrain and hindbrain.
4. 6 weeks: the neural tube has differentiated into the brain regions that are present at birth.
The central cavity (lumen) will become the ventricles of the brain.
5. 11 weeks: The cerebrum overgrows the rest of the brain divisions. The directional references
are different for an embryo (dorsal, rostral etc).
6. 40 weeks: the rapid growth within the rigid confines of the cranium forces it to develop a
convoluted furrowed surface
7. Child: the directions “dorsal” and “ventral” are different in the child brain because of the
flexion in the neural tube during development.
The brain is encased in bony skull, or cranium. The spinal cord runs through the vertebral column →
bony vertebrae.
Gray matter:
– Unmyelinated nerve cell bodies
– Clusters of cell bodies in the CNS are nuclei
– Dendrites
– Axon terminals
White matter
– Myelinated axons
– Axon bundles connecting CNS regions are tracts
▪ Contain very few cell bodies
Dura mater and pia mater also protects the brain → tough
,There is cerebrospinal fluid in the ventricles of the brain. There are different ventricles:
• First and second ventricles form the lateral ventricles
• → connect to the third ventricle through narrow openings
• → The cerebral aqueduct then leads form the third ventricle in the diencephalon to the fourt
ventricle in the brain stem.
• → The fourth ventricle narrows to become the central canal of the spinal cord.
Cerebrospinal fluid:
• Is a salty solution similar to plasma
• Is produced by the choroid plexus in the ventricles
- Materials selectively moved plasma to ventricles
- Water follows due to osmotic gradient
• Surrounds the entire brain
- Contained within subarachnoid space (between arachnoid membrane and pia mater)
- Flows from ventricles to subarachnoid space to return to plasma by villi
• Function in physical and chemical protection
Choroid plexus:
• Transports ions and nutrients from the blood into the cerebrospinal fluid
• Produces cerebrospinal fluid
Meninges:
• The meninges and extracellular fluid cushion the delicate brain tissue
Metabolic requirements of neural tissue
• Neurons need a constant supply of oxygen and glucose
• Brain receives 15% of blood pumped by heart → a lot
• Oxygen: passes freely across blood-brain barrier
• Glucose:
- Membrane transporters move glucose from plasma into the brain interstitial fluid
- Brain responsible for about half of body’s glucose consumption
- Progressive hypoglycemia leads to confusion, unconsciousness, and death.
The blood-brain barrier:
• Highly selective permeability of brain capillaries
• Astrocytes foot processes promote tight junctions between endothelial cells
• Protects brain from toxic water soluble compounds and pathogens
• Small lipid-soluble molecules cross the blood-brain barrier
The organization of the CNS: the spinal cord:
It contains nuclei with cell bodies of efferent neurons and tracts of axons going to and from the brain.
Dorsal root: carries sensory information to CNS. Ventral root: carries motor information to muscles
and glands. It consists of the gray matter and white matter.
• Gray matter: consists of sensory and motor nuclei
• White matter: in the spinal cord, consists of tracts of axons carrying information to and from
the brain. Ascending tracts: carry sensory information to the brain. Descending tracts: carry
commands to motor neurons.
Spinal reflexes:
The sensory information entering the spinal cord is acted on without input from the brain. However,
sensory information about the stimulus may be sent to the brain.
,There is a stimulus where the sensory receptors detect pain in the skin → these nerve signals goes
through the sensory neuron in the dorsal root ganglion → relay neuron → from here there goes a
sensation relayed to the brain and an nerve signal further to the motor neuron in the ventral root →
command to muscles or glands → response.
The brain stem:
• Midbrain: eye movement, relay signals for hearing and seeing reflexes
• Cranial nerves: 11 of 12 cranial nerves originate from the brain stem, can include sensory
fibers, efferent fibers, or both (mixed nerves). Example: vagus nerve (cranial nerve X) is a
mixed nerve.
• Medulla oblongata: Controls involuntary functions: blood pressure, breathing,
swallowing, vomiting
• Pons: Relay station, coordinates control of breathing
The diencephalon:
Lies between brain stem and the cerebrum, consisting of:
• Thalamus: sensory relay station
• Pineal gland: melatonin production → role in circadian
and circannual control
• Hypothalamus:
• Control of homeostasis
• Center for behavioral drives: for example, hunger,
thirst.
• Influences autonomic and endocrine function
• Pituitary: posterior and anterior lobes → several
controls of endocrine functions
First cranial nerve from your nose does not originate from the
brain stem.
The limbic system
Is part of the gray matter of the cerebrum
• Cingulate gyrus: plays a role in emotion
• Hippocampus: is involved in learning and memory
• Amygdala: is involved in emotion and memory
Functions of the cerebrum:
The cerebrum is the site of higher brain functions and it consists of two hemispheres connected by
corpus callosum. It has a gray matter and white matter.
Gray matter
Cerebral cortex:
• Sensory areas → perception
• Motor areas → skeletal muscle movement
• Association areas → integration of information and direction of voluntary movemet
Basal ganglia:
• Movement
Limbic system:
• Emotion, memory and learning
, White matter
• Found mostly on the interior
• Bundles of fibers connecting the different regions of the brain
Functions of the cerebellum:
• Movement coordination
The motor system (governs output from the CNS)
Three major types
• Skeletal muscle movement → somatic motor division
• Neuroendocrine signals → hypothalamus and adrenal medulla
• Visceral responses → autonomic division
Voluntary movement (is the expression of thought through action)
• Primary motor cortex
• Motor association areas
The neuroendocrine and visceral responses are coordinated in the hypothalamus and medulla
Brain function
• Sensory system
• Monitors internal and external environments
• Initiates reflex response
• Cognitive system
• Initiates voluntary responses
• Behavioral state system
• Governs sleep-wake cycles and other intrinsic behaviors
