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• All vertebrates’ nervous systems show cephalization along with CNS

and PNS• Cephalization- an evolutionary trend toward the

concentration of sensory equipment on the anterior end of the body

• The spinal cord conveys information to and from the brain that trigger responses to certain stimuli.

• Unlike invertebrates, vertebrates do not contain segmental ganglia.• Instead, the segmental ganglia are outside of the

spinal cord, which shows organization

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• CNS consists of the brain and spinal cord.• The Central Nervous System is derived from the dorsal

embryonic nerve cord, which is hollow.• The feature persists through adulthood with the narrow

central canal of the spinal cord and ventricles of the brain. • Ventricles are filled with cerebrospinal fluid– formed in the brain by filtration of blood and assists the

supply of nutrients and hormones to different parts of the brain while also removing waste.

Central Nervous System

• Axons carry nerve responses away from cell body toward target cells.

• Axons in the CNS are found in bundles with a white appearance due to the myelin sheaths

• Cross sections of the brain and spinal cord make the white matter distinguishable from the grey matter.– Grey matter is mainly dendrites, unmyelinated

axons, and neuron cell bodies.

The Peripheral Nervous System

• Transmits information to and from the CNS• Regulates vertebrates movements and internal environment• Consists of cranial and spinal nerves.

– Cranial nerves originate in the brain and terminate mostly in organs of the head and upper body.

– Spinal nerves tend to parts of the body below the head and originate in the spinal cord.

• Mammals have 31 pairs of spinal nerves and 12 pairs of cranial nerves.

• The PNS can be divided into two functional components– Somatic Nervous System– Autonomic Nervous System

Somatic Nervous System

• Carries signals to and from skeletal muscles– In response to external stimuli

• Voluntary, because it is subject to conscious control, but a lot of skeletal muscle activity is controlled by reflexes mediated by the spinal cord and brain stem.

Autonomic Nervous System

• Regulates internal environment by controlling smooth and cardiac muscles and the organs of the digestive, cardiovascular, excretory, and endocrine systems

• Made up of:– Sympathetic– Parasympathetic – Enteric

Parasympathetic division vs. Sympathetic division

• Parasympathetic division causes opposite responses that promote calming and return to self-maintenance functions.

• Rest and digest• Increased activity in the parasympathetic division

causes– Increases glycogen production– Decreases heart rate – Enhances digestion

• Sympathetic and parasympathetic have antagonist effects when the neurons innervate the same organ

Enteric Division

• Consists of networks of neurons in the digestive tract, pancreas, and gallbladder

• Enteric division can function independently, but is sometimes– Regulated by parasympathetic and sympathetic

divisions • help maintain homeostasis– Such as shivering to increase hear production

Embryonic Development of the Brain

• Three bilaterally symmetric, anterior bulges of the neural tube– Forebrain, midbrain, hindbrain

• As vertebrates develop, the they are divided structurally and functionally.

Developments• Midbrain– Mesencephalon

• Hindbrain– Metencephalon – Myelencephalon

• Forebrain – Telencephalon– Diencephalon

Forebrain

• Cerebral Cortex- extends over and around much of the human brain. – Thalamus– Hypothalamus– Epithalamus

Brainstem “Lower Brain”

• Older part of evolutionary vertebrate• Made up of the medulla, oblongata, the pons,

and the midbrain• Functions– Homeostasis– Coordination of movement– Conduction of information to higher brain centers

• Medulla Oblongata – centers that control breathing, heart and blood

vessel activity, swallowing, vomiting, and digestion• Pons– regulates breathing centers in the Medulla

• Axons crossing from one side of the CNS to the other in the Medulla cause the right side of the brain to control much of the movement to the left and vise versa

Arousal and Sleep

• Attentiveness and mental alertness vary from movement to movement

• Counterpart to arousal is sleep• Controlled by several centers in the brainstem and cerebrum. • Melatonin promotes sleep and helps the body assimilate to its

environment • The reticular active system regulates sleep and arousal. – Serotonin may be the neurotransmitter of the sleep-

producing centers

The Diencephalon

• Develops into three adult brain regions. – Epithalamus: includes pineal gland and choroid plexus and

produces cerebrospinal fluid from blood– Thalamus: main input center for sensory information going

to the cerebrum and the main output center for motor information leaing the cerebrum; information from all senses is sorted in the thalamus

– Hypothalamus: source of posterior pituitary and releasing hormones that on the anterior pituitary and controls flight response and mating

Circadian Rhythms

• Biological clock is involved in maintaining circadian rhythms and a variety of physical phenomena. – Hormone release, hunger, heightened sensitivity to

external stimuli • Mammals biological clock is a pair of hypothalamic

structures called Suprachiasmatic nuclei (SCN) • Usually require external cues to remain synchronized

with environmental cycles.

Cerebrum

• Divided to left right cerebral hemispheres• Outer covering of grey matter• Inner white matter that contains basal nuclei,

or important centers for planning and learning movement sequences

• Largest and most complex part of the brain is the cerebral cortex– Sensory information is analyzed and motor

commands are issued. • Neocortex: forms the outermost part of the

mammalian cerebrum, made of of six parallel layers of neurons arranged tangential to the brain surface – Accounts for 80% of total brain mass

• Cerebral Cortex is divided into left and right halves• A thick band of axons known as the corpus

callosum enables communication between the left and right cerebral cortices

• Damage of one are of the cerebrum may cause redirection of its normal functions to other areas.

• Live can be lived with one hemisphere as seen in some infants with severe epilepsy that have entire hemispheres removed– the other hemisphere will eventually take up most of

the functions of the other hemisphere

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• The cerebral cortex controls voluntary movement and cognitive functions– Each side of the cerebral cortex has four lobes;

frontal, temporal, occipital, and parietal lobes• They are the primary sensory areas, and each

receives a specific type of sensory information

Processing

• Occipital lobe- visual• Temporal lobe- auditory • Parietal lobe- somatosensory, taste– touch, pain, pressure, temperature, and the

position of muscles and limbs• Frontal lobe- olfactory information

Lateralization of Cortical Function

• During brain development after birth, competing functions segregate and displace each other in the cortex of the left and right cerebral hemispheres

• The left hemisphere becomes more adept to language, math, logical operations, and the serial processing of sequences of information

• The right hemisphere is stronger at pattern recognition, face recognition, spatial relations, nonverbal thinking, emotional processing in general, and the simultaneous processing of many kinds of information

• Split brain causes each side of the brain to work independently, occurring when the corpus callosum is cut

Language and Speech

• Can be injured by strokes or tumors. • Karl Wernicke – Discovered that damage to a posterior portion of the

temporal temporal lobe, which is now called Wernicke’s area, destroyed the ability to comprehend speech, but the speech generator was still in tact.

• Pierre Broca– Sometimes people can understand language, but not

speak, whom were later examined and it was discovered that they had defects in a small region of the left frontal lobe, which is now known as Broca’s area

Emotions

• Results of complex interplay of many regions of the brain– Limbic system: a ring of structures around the

brainstem that includes the cerebral cortex, amygdala, and the hippocampus.• Attaches emotional “feelings” to basic survival

• Amygdala- central to recognizing the emotional content of facial expressions and laying down emotional memories.

• Hippocampus- explicit recall of events or emotional memory

• Hypothalamus and Thalamus- interact with sensory areas of the neocortex and other higher brain centers, mediating primary emotions such as laughing and crying

Memory and Learning

• Short-term memory- constantly comparing what is happening to what just happened

• Long-term memory- names or numbers are stored in long erm memory along with other data that has been permanently stored– Requiring the Hippocampus

• Wernicke’s and Broca’s areas store and retrieve words and images

• Motor skills are usually learned with repetition

Cellular Mechanisms of Learning

• Long-term potential- increase in strength of synaptic transmission that occurs when presynaptic neurons produce a brief, high frequency series of action potentials.

• LTP can last days or weeks when memories are stored. • Post synaptic neurons possess two types of glutamate

receptors – AMPA: part of ligand-gated ion channels; when glutamate

binds to them, Na+ and K+ diffuse through channels – NMDA: both ligand gated and voltage gated that open only if

glutamate is bound and the membrane is depolarized.

Consciousness

• Was thought to be a subject of philosophy or religion

• fMRI has allowed the possibility of comparing activity in the human brain different states of consciousness–Offers a detailed picture of how neural

acticty correlates with conscious experiments

Nerve Cell

• To reach target cells, axons have to elongate from a few micrometers to a meter or more

• Growth Cone- responsive region at the leading edge of the growing axon

• Axons respond by growing towards or away with attraction and repulsion

Neural Stem Cells

• Human brain produces new neurons• Ericksson: found newly divided neurons in the

hippocampus of all the patients of a cancer study

• Mature neurons are unable to undergo cell division

• Progenitor- fact that stem cells are committed to becoming either neurons or glia

Diseases and Disorders of the Nervous System

• Schizophrenia- severe mental disturbance characterized by psychotic episodes in which patients lose the ability to distinguish reality– Dopamine

• Depression• Bipolar Disorder- swings of mood from high to low and affects about 1% of

the world’s population• Major depression- have a low mood most of the time; they constitute roughly

5% of the population

• Alzheimer’s Disease- mental deterioration, or dementia, characterized by confusion, memory loss, and a variety of other symptoms. It rises from 10% at age 65 and 35% at age 85.

• AD is difficult to make while the patient is alive because it is a form of dementia.

• Parkinson’s Disease- a motor disorder characterized by difficulty in initiating movements, slowness of movements. And rigidity.

• Patients of PD often have masked facial expression, muscle tremors, poor balance, flexed posture, and a shuffling gait. • L-Dopa